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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<title>Modifying document data</title>
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<td>pugixml 0.9 manual |
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<hr>
<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="manual.modify"></a><a class="link" href="modify.html" title="Modifying document data"> Modifying document data</a>
</h2></div></div></div>
<div class="toc"><dl>
<dt><span class="section"><a href="modify.html#manual.modify.nodedata"> Setting node data</a></span></dt>
<dt><span class="section"><a href="modify.html#manual.modify.attrdata"> Setting attribute data</a></span></dt>
<dt><span class="section"><a href="modify.html#manual.modify.add"> Adding nodes/attributes</a></span></dt>
<dt><span class="section"><a href="modify.html#manual.modify.remove"> Removing nodes/attributes</a></span></dt>
<dt><span class="section"><a href="modify.html#manual.modify.clone"> Cloning nodes/attributes</a></span></dt>
</dl></div>
<p>
The document in pugixml is fully mutable: you can completely change the document
structure and modify the data of nodes/attributes. This section provides documentation
for the relevant functions. All functions take care of memory management and
structural integrity themselves, so they always result in structurally valid
tree - however, it is possible to create an invalid XML tree (for example,
by adding two attributes with the same name or by setting attribute/node name
to empty/invalid string). Tree modification is optimized for performance and
for memory consumption, so if you have enough memory you can create documents
from scratch with pugixml and later save them to file/stream instead of relying
on error-prone manual text writing and without too much overhead.
</p>
<p>
All member functions that change node/attribute data or structure are non-constant
and thus can not be called on constant handles. However, you can easily convert
constant handle to non-constant one by simple assignment: <code class="computeroutput"><span class="keyword">void</span>
<span class="identifier">foo</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span><span class="special">&</span> <span class="identifier">n</span><span class="special">)</span>
<span class="special">{</span> <span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">nc</span> <span class="special">=</span> <span class="identifier">n</span><span class="special">;</span> <span class="special">}</span></code>, so const-correctness
here mainly provides additional documentation.
</p>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="manual.modify.nodedata"></a><a class="link" href="modify.html#manual.modify.nodedata" title="Setting node data"> Setting node data</a>
</h3></div></div></div>
<a name="xml_node::set_name"></a><a name="xml_node::set_value"></a><p>
As discussed before, nodes can have name and value, both of which are strings.
Depending on node type, name or value may be absent. <code class="computeroutput"><span class="identifier">node_document</span></code>
nodes do not have name or value, <code class="computeroutput"><span class="identifier">node_element</span></code>
and <code class="computeroutput"><span class="identifier">node_declaration</span></code> nodes
always have a name but never have a value, <code class="computeroutput"><span class="identifier">node_pcdata</span></code>,
<code class="computeroutput"><span class="identifier">node_cdata</span></code> and <code class="computeroutput"><span class="identifier">node_comment</span></code> nodes never have a name but
always have a value (it may be empty though), <code class="computeroutput"><span class="identifier">node_pi</span></code>
nodes always have a name and a value (again, value may be empty). In order
to set node's name or value, you can use the following functions:
</p>
<pre class="programlisting"><span class="keyword">bool</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">set_name</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">char_t</span><span class="special">*</span> <span class="identifier">rhs</span><span class="special">);</span>
<span class="keyword">bool</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">set_value</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">char_t</span><span class="special">*</span> <span class="identifier">rhs</span><span class="special">);</span>
</pre>
<p>
Both functions try to set the name/value to the specified string, and return
the operation result. The operation fails if the node can not have name or
value (for instance, when trying to call <code class="computeroutput"><span class="identifier">set_name</span></code>
on a <code class="computeroutput"><span class="identifier">node_pcdata</span></code> node), if
the node handle is null, or if there is insufficient memory to handle the
request. The provided string is copied into document managed memory and can
be destroyed after the function returns (for example, you can safely pass
stack-allocated buffers to these functions). The name/value content is not
verified, so take care to use only valid XML names, or the document may become
malformed.
</p>
<p>
There is no equivalent of <code class="computeroutput"><span class="identifier">child_value</span></code>
function for modifying text children of the node.
</p>
<p>
This is an example of setting node name and value (<a href="../samples/modify_base.cpp" target="_top">samples/modify_base.cpp</a>):
</p>
<p>
</p>
<pre class="programlisting"><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">node</span> <span class="special">=</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">child</span><span class="special">(</span><span class="string">"node"</span><span class="special">);</span>
<span class="comment">// change node name
</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">node</span><span class="special">.</span><span class="identifier">set_name</span><span class="special">(</span><span class="string">"notnode"</span><span class="special">);</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">", new node name: "</span> <span class="special"><<</span> <span class="identifier">node</span><span class="special">.</span><span class="identifier">name</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="comment">// change comment text
</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">last_child</span><span class="special">().</span><span class="identifier">set_value</span><span class="special">(</span><span class="string">"useless comment"</span><span class="special">);</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">", new comment text: "</span> <span class="special"><<</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">last_child</span><span class="special">().</span><span class="identifier">value</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="comment">// we can't change value of the element or name of the comment
</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">node</span><span class="special">.</span><span class="identifier">set_value</span><span class="special">(</span><span class="string">"1"</span><span class="special">)</span> <span class="special"><<</span> <span class="string">", "</span> <span class="special"><<</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">last_child</span><span class="special">().</span><span class="identifier">set_name</span><span class="special">(</span><span class="string">"2"</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
</pre>
<p>
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="manual.modify.attrdata"></a><a class="link" href="modify.html#manual.modify.attrdata" title="Setting attribute data"> Setting attribute data</a>
</h3></div></div></div>
<a name="xml_attribute::set_name"></a><a name="xml_attribute::set_value"></a><p>
All attributes have name and value, both of which are strings (value may
be empty). You can set them with the following functions:
</p>
<pre class="programlisting"><span class="keyword">bool</span> <span class="identifier">xml_attribute</span><span class="special">::</span><span class="identifier">set_name</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">char_t</span><span class="special">*</span> <span class="identifier">rhs</span><span class="special">);</span>
<span class="keyword">bool</span> <span class="identifier">xml_attribute</span><span class="special">::</span><span class="identifier">set_value</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">char_t</span><span class="special">*</span> <span class="identifier">rhs</span><span class="special">);</span>
</pre>
<p>
Both functions try to set the name/value to the specified string, and return
the operation result. The operation fails if the attribute handle is null,
or if there is insufficient memory to handle the request. The provided string
is copied into document managed memory and can be destroyed after the function
returns (for example, you can safely pass stack-allocated buffers to these
functions). The name/value content is not verified, so take care to use only
valid XML names, or the document may become malformed.
</p>
<p>
In addition to string functions, several functions are provided for handling
attributes with numbers and booleans as values:
</p>
<pre class="programlisting"><span class="keyword">bool</span> <span class="identifier">xml_attribute</span><span class="special">::</span><span class="identifier">set_value</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">rhs</span><span class="special">);</span>
<span class="keyword">bool</span> <span class="identifier">xml_attribute</span><span class="special">::</span><span class="identifier">set_value</span><span class="special">(</span><span class="keyword">unsigned</span> <span class="keyword">int</span> <span class="identifier">rhs</span><span class="special">);</span>
<span class="keyword">bool</span> <span class="identifier">xml_attribute</span><span class="special">::</span><span class="identifier">set_value</span><span class="special">(</span><span class="keyword">double</span> <span class="identifier">rhs</span><span class="special">);</span>
<span class="keyword">bool</span> <span class="identifier">xml_attribute</span><span class="special">::</span><span class="identifier">set_value</span><span class="special">(</span><span class="keyword">bool</span> <span class="identifier">rhs</span><span class="special">);</span>
</pre>
<p>
The above functions convert the argument to string and then call the base
<code class="computeroutput"><span class="identifier">set_value</span></code> function. Integers
are converted to a decimal form, floating-point numbers are converted to
either decimal or scientific form, depending on the number magnitude, boolean
values are converted to either <code class="computeroutput"><span class="string">"true"</span></code>
or <code class="computeroutput"><span class="string">"false"</span></code>.
</p>
<div class="caution"><table border="0" summary="Caution">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="../images/caution.png"></td>
<th align="left">Caution</th>
</tr>
<tr><td align="left" valign="top"><p>
Number conversion functions depend on current C locale as set with <code class="computeroutput"><span class="identifier">setlocale</span></code>, so may generate unexpected
results if the locale is different from <code class="computeroutput"><span class="string">"C"</span></code>.
</p></td></tr>
</table></div>
<div class="note"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../images/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top"><p>
There are no portable 64-bit types in C++, so there is no corresponding
<code class="computeroutput"><span class="identifier">set_value</span></code> function. If
your platform has a 64-bit integer, you can easily write such a function
yourself.
</p></td></tr>
</table></div>
<a name="xml_attribute::assign"></a><p>
For convenience, all <code class="computeroutput"><span class="identifier">set_value</span></code>
functions have the corresponding assignment operators:
</p>
<pre class="programlisting"><span class="identifier">xml_attribute</span><span class="special">&</span> <span class="identifier">xml_attribute</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span><span class="keyword">const</span> <span class="identifier">char_t</span><span class="special">*</span> <span class="identifier">rhs</span><span class="special">);</span>
<span class="identifier">xml_attribute</span><span class="special">&</span> <span class="identifier">xml_attribute</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span><span class="keyword">int</span> <span class="identifier">rhs</span><span class="special">);</span>
<span class="identifier">xml_attribute</span><span class="special">&</span> <span class="identifier">xml_attribute</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span><span class="keyword">unsigned</span> <span class="keyword">int</span> <span class="identifier">rhs</span><span class="special">);</span>
<span class="identifier">xml_attribute</span><span class="special">&</span> <span class="identifier">xml_attribute</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span><span class="keyword">double</span> <span class="identifier">rhs</span><span class="special">);</span>
<span class="identifier">xml_attribute</span><span class="special">&</span> <span class="identifier">xml_attribute</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span><span class="keyword">bool</span> <span class="identifier">rhs</span><span class="special">);</span>
</pre>
<p>
These operators simply call the right <code class="computeroutput"><span class="identifier">set_value</span></code>
function and return the attribute they're called on; the return value of
<code class="computeroutput"><span class="identifier">set_value</span></code> is ignored, so
errors are not detected.
</p>
<p>
This is an example of setting attribute name and value (<a href="../samples/modify_base.cpp" target="_top">samples/modify_base.cpp</a>):
</p>
<p>
</p>
<pre class="programlisting"><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_attribute</span> <span class="identifier">attr</span> <span class="special">=</span> <span class="identifier">node</span><span class="special">.</span><span class="identifier">attribute</span><span class="special">(</span><span class="string">"id"</span><span class="special">);</span>
<span class="comment">// change attribute name/value
</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">attr</span><span class="special">.</span><span class="identifier">set_name</span><span class="special">(</span><span class="string">"key"</span><span class="special">)</span> <span class="special"><<</span> <span class="string">", "</span> <span class="special"><<</span> <span class="identifier">attr</span><span class="special">.</span><span class="identifier">set_value</span><span class="special">(</span><span class="string">"345"</span><span class="special">);</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">", new attribute: "</span> <span class="special"><<</span> <span class="identifier">attr</span><span class="special">.</span><span class="identifier">name</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"="</span> <span class="special"><<</span> <span class="identifier">attr</span><span class="special">.</span><span class="identifier">value</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="comment">// we can use numbers or booleans
</span><span class="identifier">attr</span><span class="special">.</span><span class="identifier">set_value</span><span class="special">(</span><span class="number">1.234</span><span class="special">);</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"new attribute value: "</span> <span class="special"><<</span> <span class="identifier">attr</span><span class="special">.</span><span class="identifier">value</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="comment">// we can also use assignment operators for more concise code
</span><span class="identifier">attr</span> <span class="special">=</span> <span class="keyword">true</span><span class="special">;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"final attribute value: "</span> <span class="special"><<</span> <span class="identifier">attr</span><span class="special">.</span><span class="identifier">value</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
</pre>
<p>
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="manual.modify.add"></a><a class="link" href="modify.html#manual.modify.add" title="Adding nodes/attributes"> Adding nodes/attributes</a>
</h3></div></div></div>
<a name="xml_node::append_attribute"></a><a name="xml_node::insert_attribute_after"></a><a name="xml_node::insert_attribute_before"></a><a name="xml_node::append_child"></a><a name="xml_node::insert_child_after"></a><a name="xml_node::insert_child_before"></a><p>
Nodes and attributes do not exist outside of document tree, so you can't
create them without adding them to some document. A node or attribute can
be created at the end of node/attribute list or before/after some other node:
</p>
<pre class="programlisting"><span class="identifier">xml_attribute</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">append_attribute</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">char_t</span><span class="special">*</span> <span class="identifier">name</span><span class="special">);</span>
<span class="identifier">xml_attribute</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">insert_attribute_after</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">char_t</span><span class="special">*</span> <span class="identifier">name</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">xml_attribute</span><span class="special">&</span> <span class="identifier">attr</span><span class="special">);</span>
<span class="identifier">xml_attribute</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">insert_attribute_before</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">char_t</span><span class="special">*</span> <span class="identifier">name</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">xml_attribute</span><span class="special">&</span> <span class="identifier">attr</span><span class="special">);</span>
<span class="identifier">xml_node</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">append_child</span><span class="special">(</span><span class="identifier">xml_node_type</span> <span class="identifier">type</span> <span class="special">=</span> <span class="identifier">node_element</span><span class="special">);</span>
<span class="identifier">xml_node</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">insert_child_after</span><span class="special">(</span><span class="identifier">xml_node_type</span> <span class="identifier">type</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">xml_node</span><span class="special">&</span> <span class="identifier">node</span><span class="special">);</span>
<span class="identifier">xml_node</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">insert_child_before</span><span class="special">(</span><span class="identifier">xml_node_type</span> <span class="identifier">type</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">xml_node</span><span class="special">&</span> <span class="identifier">node</span><span class="special">);</span>
</pre>
<p>
<code class="computeroutput"><span class="identifier">append_attribute</span></code> and <code class="computeroutput"><span class="identifier">append_child</span></code> create a new node/attribute
at the end of the corresponding list of the node the method is called on;
<code class="computeroutput"><span class="identifier">insert_attribute_after</span></code>,
<code class="computeroutput"><span class="identifier">insert_attribute_before</span></code>,
<code class="computeroutput"><span class="identifier">insert_child_after</span></code> and <code class="computeroutput"><span class="identifier">insert_attribute_before</span></code> add the node/attribute
before or after specified node/attribute.
</p>
<p>
Attribute functions create an attribute with the specified name; you can
specify the empty name and change the name later if you want to. Node functions
create the node with the specified type; since node type can't be changed,
you have to know the desired type beforehand. Also note that not all types
can be added as children; see below for clarification.
</p>
<p>
All functions return the handle to newly created object on success, and null
handle on failure. There are several reasons for failure:
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
Adding fails if the target node is null;
</li>
<li class="listitem">
Only <code class="computeroutput"><span class="identifier">node_element</span></code> nodes
can contain attributes, so attribute adding fails if node is not an element;
</li>
<li class="listitem">
Only <code class="computeroutput"><span class="identifier">node_document</span></code> and
<code class="computeroutput"><span class="identifier">node_element</span></code> nodes can
contain children, so child node adding fails if target node is not an
element or a document;
</li>
<li class="listitem">
<code class="computeroutput"><span class="identifier">node_document</span></code> and <code class="computeroutput"><span class="identifier">node_null</span></code> nodes can not be inserted
as children, so passing <code class="computeroutput"><span class="identifier">node_document</span></code>
or <code class="computeroutput"><span class="identifier">node_null</span></code> value as
type results in operation failure;
</li>
<li class="listitem">
<code class="computeroutput"><span class="identifier">node_declaration</span></code> nodes
can only be added as children of the document node; attempt to insert
declaration node as a child of an element node fails;
</li>
<li class="listitem">
Adding node/attribute results in memory allocation, which may fail;
</li>
<li class="listitem">
Insertion functions fail if the specified node or attribute is not in
the target node's children/attribute list.
</li>
</ul></div>
<p>
Even if the operation fails, the document remains in consistent state, but
the requested node/attribute is not added.
</p>
<div class="caution"><table border="0" summary="Caution">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="../images/caution.png"></td>
<th align="left">Caution</th>
</tr>
<tr><td align="left" valign="top"><p>
attribute() and child() functions do not add attributes or nodes to the
tree, so code like <code class="computeroutput"><span class="identifier">node</span><span class="special">.</span><span class="identifier">attribute</span><span class="special">(</span><span class="string">"id"</span><span class="special">)</span> <span class="special">=</span> <span class="number">123</span><span class="special">;</span></code> will not do anything if <code class="computeroutput"><span class="identifier">node</span></code> does not have an attribute with
name <code class="computeroutput"><span class="string">"id"</span></code>. Make sure
you're operating with existing attributes/nodes by adding them if necessary.
</p></td></tr>
</table></div>
<p>
This is an example of adding new attributes/nodes to the document (<a href="../samples/modify_add.cpp" target="_top">samples/modify_add.cpp</a>):
</p>
<p>
</p>
<pre class="programlisting"><span class="comment">// add node with some name
</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">node</span> <span class="special">=</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">append_child</span><span class="special">();</span>
<span class="identifier">node</span><span class="special">.</span><span class="identifier">set_name</span><span class="special">(</span><span class="string">"node"</span><span class="special">);</span>
<span class="comment">// add description node with text child
</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">descr</span> <span class="special">=</span> <span class="identifier">node</span><span class="special">.</span><span class="identifier">append_child</span><span class="special">();</span>
<span class="identifier">descr</span><span class="special">.</span><span class="identifier">set_name</span><span class="special">(</span><span class="string">"description"</span><span class="special">);</span>
<span class="identifier">descr</span><span class="special">.</span><span class="identifier">append_child</span><span class="special">(</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">node_pcdata</span><span class="special">).</span><span class="identifier">set_value</span><span class="special">(</span><span class="string">"Simple node"</span><span class="special">);</span>
<span class="comment">// add param node before the description
</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">param</span> <span class="special">=</span> <span class="identifier">node</span><span class="special">.</span><span class="identifier">insert_child_before</span><span class="special">(</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">node_element</span><span class="special">,</span> <span class="identifier">descr</span><span class="special">);</span>
<span class="identifier">param</span><span class="special">.</span><span class="identifier">set_name</span><span class="special">(</span><span class="string">"param"</span><span class="special">);</span>
<span class="comment">// add attributes to param node
</span><span class="identifier">param</span><span class="special">.</span><span class="identifier">append_attribute</span><span class="special">(</span><span class="string">"name"</span><span class="special">)</span> <span class="special">=</span> <span class="string">"version"</span><span class="special">;</span>
<span class="identifier">param</span><span class="special">.</span><span class="identifier">append_attribute</span><span class="special">(</span><span class="string">"value"</span><span class="special">)</span> <span class="special">=</span> <span class="number">1.1</span><span class="special">;</span>
<span class="identifier">param</span><span class="special">.</span><span class="identifier">insert_attribute_after</span><span class="special">(</span><span class="string">"type"</span><span class="special">,</span> <span class="identifier">param</span><span class="special">.</span><span class="identifier">attribute</span><span class="special">(</span><span class="string">"name"</span><span class="special">))</span> <span class="special">=</span> <span class="string">"float"</span><span class="special">;</span>
</pre>
<p>
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="manual.modify.remove"></a><a class="link" href="modify.html#manual.modify.remove" title="Removing nodes/attributes"> Removing nodes/attributes</a>
</h3></div></div></div>
<a name="xml_node::remove_attribute"></a><a name="xml_node::remove_child"></a><p>
If you do not want your document to contain some node or attribute, you can
remove it with one of the following functions:
</p>
<pre class="programlisting"><span class="keyword">bool</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">remove_attribute</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">xml_attribute</span><span class="special">&</span> <span class="identifier">a</span><span class="special">);</span>
<span class="keyword">bool</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">remove_child</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">xml_node</span><span class="special">&</span> <span class="identifier">n</span><span class="special">);</span>
</pre>
<p>
<code class="computeroutput"><span class="identifier">remove_attribute</span></code> removes
the attribute from the attribute list of the node, and returns the operation
result. <code class="computeroutput"><span class="identifier">remove_child</span></code> removes
the child node with the entire subtree (including all descendant nodes and
attributes) from the document, and returns the operation result. Removing
fails if one of the following is true:
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
The node the function is called on is null;
</li>
<li class="listitem">
The attribute/node to be removed is null;
</li>
<li class="listitem">
The attribute/node to be removed is not in the node's attribute/child
list.
</li>
</ul></div>
<p>
Removing the attribute or node invalidates all handles to the same underlying
object, and also invalidates all iterators pointing to the same object. Removing
node also invalidates all past-the-end iterators to its attribute or child
node list. Be careful to ensure that all such handles and iterators either
do not exist or are not used after the attribute/node is removed.
</p>
<p>
If you want to remove the attribute or child node by its name, two additional
helper functions are available:
</p>
<pre class="programlisting"><span class="keyword">bool</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">remove_attribute</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">char_t</span><span class="special">*</span> <span class="identifier">name</span><span class="special">);</span>
<span class="keyword">bool</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">remove_child</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">char_t</span><span class="special">*</span> <span class="identifier">name</span><span class="special">);</span>
</pre>
<p>
These functions look for the first attribute or child with the specified
name, and then remove it, returning the result. If there is no attribute
or child with such name, the function returns <code class="computeroutput"><span class="keyword">false</span></code>;
if there are two nodes with the given name, only the first node is deleted.
If you want to delete all nodes with the specified name, you can use code
like this: <code class="computeroutput"><span class="keyword">while</span> <span class="special">(</span><span class="identifier">node</span><span class="special">.</span><span class="identifier">remove_child</span><span class="special">(</span><span class="string">"tool"</span><span class="special">))</span> <span class="special">;</span></code>.
</p>
<p>
This is an example of removing attributes/nodes from the document (<a href="../samples/modify_remove.cpp" target="_top">samples/modify_remove.cpp</a>):
</p>
<p>
</p>
<pre class="programlisting"><span class="comment">// remove description node with the whole subtree
</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">node</span> <span class="special">=</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">child</span><span class="special">(</span><span class="string">"node"</span><span class="special">);</span>
<span class="identifier">node</span><span class="special">.</span><span class="identifier">remove_child</span><span class="special">(</span><span class="string">"description"</span><span class="special">);</span>
<span class="comment">// remove id attribute
</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">param</span> <span class="special">=</span> <span class="identifier">node</span><span class="special">.</span><span class="identifier">child</span><span class="special">(</span><span class="string">"param"</span><span class="special">);</span>
<span class="identifier">param</span><span class="special">.</span><span class="identifier">remove_attribute</span><span class="special">(</span><span class="string">"value"</span><span class="special">);</span>
<span class="comment">// we can also remove nodes/attributes by handles
</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_attribute</span> <span class="identifier">id</span> <span class="special">=</span> <span class="identifier">param</span><span class="special">.</span><span class="identifier">attribute</span><span class="special">(</span><span class="string">"name"</span><span class="special">);</span>
<span class="identifier">param</span><span class="special">.</span><span class="identifier">remove_attribute</span><span class="special">(</span><span class="identifier">id</span><span class="special">);</span>
</pre>
<p>
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="manual.modify.clone"></a><a class="link" href="modify.html#manual.modify.clone" title="Cloning nodes/attributes"> Cloning nodes/attributes</a>
</h3></div></div></div>
<a name="xml_node::append_copy"></a><a name="xml_node::insert_copy_after"></a><a name="xml_node::insert_copy_before"></a><p>
With the help of previously described functions, it is possible to create
trees with any contents and structure, including cloning the existing data.
However since this is an often needed operation, pugixml provides built-in
node/attribute cloning facilities. Since nodes and attributes do not exist
outside of document tree, you can't create a standalone copy - you have to
immediately insert it somewhere in the tree. For this, you can use one of
the following functions:
</p>
<pre class="programlisting"><span class="identifier">xml_attribute</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">append_copy</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">xml_attribute</span><span class="special">&</span> <span class="identifier">proto</span><span class="special">);</span>
<span class="identifier">xml_attribute</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">insert_copy_after</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">xml_attribute</span><span class="special">&</span> <span class="identifier">proto</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">xml_attribute</span><span class="special">&</span> <span class="identifier">attr</span><span class="special">);</span>
<span class="identifier">xml_attribute</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">insert_copy_before</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">xml_attribute</span><span class="special">&</span> <span class="identifier">proto</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">xml_attribute</span><span class="special">&</span> <span class="identifier">attr</span><span class="special">);</span>
<span class="identifier">xml_node</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">append_copy</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">xml_node</span><span class="special">&</span> <span class="identifier">proto</span><span class="special">);</span>
<span class="identifier">xml_node</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">insert_copy_after</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">xml_node</span><span class="special">&</span> <span class="identifier">proto</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">xml_node</span><span class="special">&</span> <span class="identifier">node</span><span class="special">);</span>
<span class="identifier">xml_node</span> <span class="identifier">xml_node</span><span class="special">::</span><span class="identifier">insert_copy_before</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">xml_node</span><span class="special">&</span> <span class="identifier">proto</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">xml_node</span><span class="special">&</span> <span class="identifier">node</span><span class="special">);</span>
</pre>
<p>
These functions mirror the structure of <code class="computeroutput"><span class="identifier">append_child</span></code>,
<code class="computeroutput"><span class="identifier">insert_child_before</span></code> and related
functions - they take the handle to the prototype object, which is to be
cloned, insert a new attribute/node at the appropriate place, and then copy
the attribute data or the whole node subtree to the new object. The functions
return the handle to the resulting duplicate object, or null handle on failure.
</p>
<p>
The attribute is copied along with the name and value; the node is copied
along with its type, name and value; additionally attribute list and all
children are recursively cloned, resulting in the deep subtree clone. The
prototype object can be a part of the same document, or a part of any other
document.
</p>
<p>
The failure conditions resemble those of <code class="computeroutput"><span class="identifier">append_child</span></code>,
<code class="computeroutput"><span class="identifier">insert_child_before</span></code> and related
functions, <a class="link" href="modify.html#xml_node::append_child">consult their documentation
for more information</a>. There are additional caveats specific to cloning
functions:
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
Cloning null handles results in operation failure;
</li>
<li class="listitem">
Node cloning starts with insertion of the node of the same type as that
of the prototype; for this reason, cloning functions can not be directly
used to clone entire documents, since <code class="computeroutput"><span class="identifier">node_document</span></code>
is not a valid insertion type. The example below provides a workaround.
</li>
<li class="listitem">
It is possible to copy a subtree as a child of some node inside this
subtree, i.e. <code class="computeroutput"><span class="identifier">node</span><span class="special">.</span><span class="identifier">append_copy</span><span class="special">(</span><span class="identifier">node</span><span class="special">.</span><span class="identifier">parent</span><span class="special">().</span><span class="identifier">parent</span><span class="special">());</span></code>.
This is a valid operation, and it results in a clone of the subtree in
the state before cloning started, i.e. no infinite recursion takes place.
</li>
</ul></div>
<p>
This is an example with one possible implementation of include tags in XML
(<a href="../samples/include.cpp" target="_top">samples/include.cpp</a>). It illustrates
node cloning and usage of other document modification functions:
</p>
<p>
</p>
<pre class="programlisting"><span class="keyword">bool</span> <span class="identifier">load_preprocess</span><span class="special">(</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_document</span><span class="special">&</span> <span class="identifier">doc</span><span class="special">,</span> <span class="keyword">const</span> <span class="keyword">char</span><span class="special">*</span> <span class="identifier">path</span><span class="special">);</span>
<span class="keyword">bool</span> <span class="identifier">preprocess</span><span class="special">(</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">node</span><span class="special">)</span>
<span class="special">{</span>
<span class="keyword">for</span> <span class="special">(</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">child</span> <span class="special">=</span> <span class="identifier">node</span><span class="special">.</span><span class="identifier">first_child</span><span class="special">();</span> <span class="identifier">child</span><span class="special">;</span> <span class="special">)</span>
<span class="special">{</span>
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">child</span><span class="special">.</span><span class="identifier">type</span><span class="special">()</span> <span class="special">==</span> <span class="identifier">pugi</span><span class="special">::</span><span class="identifier">node_pi</span> <span class="special">&&</span> <span class="identifier">strcmp</span><span class="special">(</span><span class="identifier">child</span><span class="special">.</span><span class="identifier">name</span><span class="special">(),</span> <span class="string">"include"</span><span class="special">)</span> <span class="special">==</span> <span class="number">0</span><span class="special">)</span>
<span class="special">{</span>
<span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">include</span> <span class="special">=</span> <span class="identifier">child</span><span class="special">;</span>
<span class="comment">// load new preprocessed document (note: ideally this should handle relative paths)
</span> <span class="keyword">const</span> <span class="keyword">char</span><span class="special">*</span> <span class="identifier">path</span> <span class="special">=</span> <span class="identifier">include</span><span class="special">.</span><span class="identifier">value</span><span class="special">();</span>
<span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_document</span> <span class="identifier">doc</span><span class="special">;</span>
<span class="keyword">if</span> <span class="special">(!</span><span class="identifier">load_preprocess</span><span class="special">(</span><span class="identifier">doc</span><span class="special">,</span> <span class="identifier">path</span><span class="special">))</span> <span class="keyword">return</span> <span class="keyword">false</span><span class="special">;</span>
<span class="comment">// insert the comment marker above include directive
</span> <span class="identifier">node</span><span class="special">.</span><span class="identifier">insert_child_before</span><span class="special">(</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">node_comment</span><span class="special">,</span> <span class="identifier">include</span><span class="special">).</span><span class="identifier">set_value</span><span class="special">(</span><span class="identifier">path</span><span class="special">);</span>
<span class="comment">// copy the document above the include directive (this retains the original order!)
</span> <span class="keyword">for</span> <span class="special">(</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_node</span> <span class="identifier">ic</span> <span class="special">=</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">first_child</span><span class="special">();</span> <span class="identifier">ic</span><span class="special">;</span> <span class="identifier">ic</span> <span class="special">=</span> <span class="identifier">ic</span><span class="special">.</span><span class="identifier">next_sibling</span><span class="special">())</span>
<span class="special">{</span>
<span class="identifier">node</span><span class="special">.</span><span class="identifier">insert_copy_before</span><span class="special">(</span><span class="identifier">ic</span><span class="special">,</span> <span class="identifier">include</span><span class="special">);</span>
<span class="special">}</span>
<span class="comment">// remove the include node and move to the next child
</span> <span class="identifier">child</span> <span class="special">=</span> <span class="identifier">child</span><span class="special">.</span><span class="identifier">next_sibling</span><span class="special">();</span>
<span class="identifier">node</span><span class="special">.</span><span class="identifier">remove_child</span><span class="special">(</span><span class="identifier">include</span><span class="special">);</span>
<span class="special">}</span>
<span class="keyword">else</span>
<span class="special">{</span>
<span class="keyword">if</span> <span class="special">(!</span><span class="identifier">preprocess</span><span class="special">(</span><span class="identifier">child</span><span class="special">))</span> <span class="keyword">return</span> <span class="keyword">false</span><span class="special">;</span>
<span class="identifier">child</span> <span class="special">=</span> <span class="identifier">child</span><span class="special">.</span><span class="identifier">next_sibling</span><span class="special">();</span>
<span class="special">}</span>
<span class="special">}</span>
<span class="keyword">return</span> <span class="keyword">true</span><span class="special">;</span>
<span class="special">}</span>
<span class="keyword">bool</span> <span class="identifier">load_preprocess</span><span class="special">(</span><span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_document</span><span class="special">&</span> <span class="identifier">doc</span><span class="special">,</span> <span class="keyword">const</span> <span class="keyword">char</span><span class="special">*</span> <span class="identifier">path</span><span class="special">)</span>
<span class="special">{</span>
<span class="identifier">pugi</span><span class="special">::</span><span class="identifier">xml_parse_result</span> <span class="identifier">result</span> <span class="special">=</span> <span class="identifier">doc</span><span class="special">.</span><span class="identifier">load_file</span><span class="special">(</span><span class="identifier">path</span><span class="special">,</span> <span class="identifier">pugi</span><span class="special">::</span><span class="identifier">parse_default</span> <span class="special">|</span> <span class="identifier">pugi</span><span class="special">::</span><span class="identifier">parse_pi</span><span class="special">);</span> <span class="comment">// for <?include?>
</span>
<span class="keyword">return</span> <span class="identifier">result</span> <span class="special">?</span> <span class="identifier">preprocess</span><span class="special">(</span><span class="identifier">doc</span><span class="special">)</span> <span class="special">:</span> <span class="keyword">false</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
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