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<td >Qt 5.9</td><td ><a href="qtcore-index.html">Qt Core</a></td><td ><a href="qtcore-module.html">C++ Classes</a></td><td >QSharedDataPointer</td></tr></table><table class="buildversion"><tr>
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<h3><a name="toc">Contents</a></h3>
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<li class="level1"><a href="#public-types">Public Types</a></li>
<li class="level1"><a href="#public-functions">Public Functions</a></li>
<li class="level1"><a href="#protected-functions">Protected Functions</a></li>
<li class="level1"><a href="#details">Detailed Description</a></li>
<li class="level2"><a href="#implicit-vs-explicit-sharing">Implicit vs Explicit Sharing</a></li>
<li class="level2"><a href="#optimize-performance-for-usage-in-qt-containers">Optimize Performance for Usage in Qt Containers</a></li>
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<h1 class="title">QSharedDataPointer Class</h1>
<!-- $$$QSharedDataPointer-brief -->
<p>The <a href="qshareddatapointer.html">QSharedDataPointer</a> class represents a pointer to an implicitly shared object. <a href="#details">More...</a></p>
<!-- @@@QSharedDataPointer -->
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> Header:</td><td class="memItemRight bottomAlign"> <span class="preprocessor">#include <QSharedDataPointer></span>
</td></tr><tr><td class="memItemLeft rightAlign topAlign"> qmake:</td><td class="memItemRight bottomAlign"> QT += core</td></tr><tr><td class="memItemLeft rightAlign topAlign"> Since:</td><td class="memItemRight bottomAlign"> Qt 4.0</td></tr></table></div><ul>
<li><a href="qshareddatapointer-members.html">List of all members, including inherited members</a></li>
</ul>
<p><b>Note:</b> All functions in this class are reentrant.</p>
<a name="public-types"></a>
<h2 id="public-types">Public Types</h2>
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> typedef </td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#Type-typedef">Type</a></b></td></tr>
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<a name="public-functions"></a>
<h2 id="public-functions">Public Functions</h2>
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#QSharedDataPointer">QSharedDataPointer</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#QSharedDataPointer-1">QSharedDataPointer</a></b>(T *<i>sharedData</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#QSharedDataPointer-2">QSharedDataPointer</a></b>(const QSharedDataPointer<T> &<i>other</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#QSharedDataPointer-3">QSharedDataPointer</a></b>(QSharedDataPointer &&<i>o</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#dtor.QSharedDataPointer">~QSharedDataPointer</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> const T *</td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#constData">constData</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> T *</td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#data">data</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> const T *</td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#data-1">data</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#detach">detach</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#swap">swap</a></b>(QSharedDataPointer &<i>other</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#operator-T--2a">operator T *</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#operator-const-T--2a">operator const T *</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#operator-not">operator!</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#operator-not-eq">operator!=</a></b>(const QSharedDataPointer<T> &<i>other</i>) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> T &</td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#operator-2a">operator*</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> const T &</td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#operator-2a-1">operator*</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> T *</td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#operator--gt">operator-></a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> const T *</td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#operator--gt-1">operator-></a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QSharedDataPointer<T> &</td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#operator-eq">operator=</a></b>(const QSharedDataPointer<T> &<i>other</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QSharedDataPointer &</td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#operator-eq-1">operator=</a></b>(T *<i>sharedData</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QSharedDataPointer<T> &</td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#operator-eq-2">operator=</a></b>(QSharedDataPointer<T> &&<i>other</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#operator-eq-eq">operator==</a></b>(const QSharedDataPointer<T> &<i>other</i>) const</td></tr>
</table></div>
<a name="protected-functions"></a>
<h2 id="protected-functions">Protected Functions</h2>
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> T *</td><td class="memItemRight bottomAlign"><b><a href="qshareddatapointer.html#clone">clone</a></b>()</td></tr>
</table></div>
<a name="details"></a>
<!-- $$$QSharedDataPointer-description -->
<div class="descr">
<h2 id="details">Detailed Description</h2>
<p>The <a href="qshareddatapointer.html">QSharedDataPointer</a> class represents a pointer to an implicitly shared object.</p>
<p><a href="qshareddatapointer.html">QSharedDataPointer</a><T> makes writing your own <a href="implicit-sharing.html">implicitly shared</a> classes easy. <a href="qshareddatapointer.html">QSharedDataPointer</a> implements thread-safe reference counting, ensuring that adding QSharedDataPointers to your reentrant classes won't make them non-reentrant.</p>
<p><a href="implicit-sharing.html">Implicit sharing</a> is used by many Qt classes to combine the speed and memory efficiency of pointers with the ease of use of classes. See the <a href="implicit-sharing.html">Shared Classes</a> page for more information.</p>
<a name="employee-example"></a><p>Suppose you want to make an <code>Employee</code> class implicitly shared. The procedure is:</p>
<ul>
<li>Define the class <code>Employee</code> to have a single data member of type <code>QSharedDataPointer<EmployeeData></code>.</li>
<li>Define the <code>EmployeeData</code> class derived from <a href="qshareddata.html">QSharedData</a> to contain all the data members you would normally have put in the <code>Employee</code> class.</li>
</ul>
<p>To show this in practice, we review the source code for the implicitly shared <code>Employee</code> class. In the header file we define the two classes <code>Employee</code> and <code>EmployeeData</code>.</p>
<pre class="cpp">
<span class="preprocessor">#include <QSharedData></span>
<span class="preprocessor">#include <QString></span>
<span class="keyword">class</span> EmployeeData : <span class="keyword">public</span> <span class="type"><a href="qshareddata.html">QSharedData</a></span>
{
<span class="keyword">public</span>:
EmployeeData() : id(<span class="operator">-</span><span class="number">1</span>) { }
EmployeeData(<span class="keyword">const</span> EmployeeData <span class="operator">&</span>other)
: <span class="type"><a href="qshareddata.html">QSharedData</a></span>(other)<span class="operator">,</span> id(other<span class="operator">.</span>id)<span class="operator">,</span> name(other<span class="operator">.</span>name) { }
<span class="operator">~</span>EmployeeData() { }
<span class="type">int</span> id;
<span class="type"><a href="qstring.html">QString</a></span> name;
};
<span class="keyword">class</span> Employee
{
<span class="keyword">public</span>:
Employee() { d <span class="operator">=</span> <span class="keyword">new</span> EmployeeData; }
Employee(<span class="type">int</span> id<span class="operator">,</span> <span class="keyword">const</span> <span class="type"><a href="qstring.html">QString</a></span> <span class="operator">&</span>name) {
d <span class="operator">=</span> <span class="keyword">new</span> EmployeeData;
setId(id);
setName(name);
}
Employee(<span class="keyword">const</span> Employee <span class="operator">&</span>other)
: d (other<span class="operator">.</span>d)
{
}
<span class="type">void</span> setId(<span class="type">int</span> id) { d<span class="operator">-</span><span class="operator">></span>id <span class="operator">=</span> id; }
<span class="type">void</span> setName(<span class="keyword">const</span> <span class="type"><a href="qstring.html">QString</a></span> <span class="operator">&</span>name) { d<span class="operator">-</span><span class="operator">></span>name <span class="operator">=</span> name; }
<span class="type">int</span> id() <span class="keyword">const</span> { <span class="keyword">return</span> d<span class="operator">-</span><span class="operator">></span>id; }
<span class="type"><a href="qstring.html">QString</a></span> name() <span class="keyword">const</span> { <span class="keyword">return</span> d<span class="operator">-</span><span class="operator">></span>name; }
<span class="keyword">private</span>:
<span class="type"><a href="qshareddatapointer.html#QSharedDataPointer">QSharedDataPointer</a></span><span class="operator"><</span>EmployeeData<span class="operator">></span> d;
};
</pre>
<p>In class <code>Employee</code>, note the single data member, a <i>d pointer</i> of type <code>QSharedDataPointer<EmployeeData></code>. All accesses of employee data must go through the <i>d pointer's</i> <code>operator->()</code>. For write accesses, <code>operator->()</code> will automatically call <a href="qshareddatapointer.html#detach">detach</a>(), which creates a copy of the shared data object if the shared data object's reference count is greater than 1. This ensures that writes to one <code>Employee</code> object don't affect any other <code>Employee</code> objects that share the same <code>EmployeeData</code> object.</p>
<p>Class <code>EmployeeData</code> inherits <a href="qshareddata.html">QSharedData</a>, which provides the <i>behind the scenes</i> reference counter. <code>EmployeeData</code> has a default constructor, a copy constructor, and a destructor. Normally, trivial implementations of these are all that is needed in the <i>data</i> class for an implicitly shared class.</p>
<p>Implementing the two constructors for class <code>Employee</code> is also straightforward. Both create a new instance of <code>EmployeeData</code> and assign it to the <i>d pointer</i> .</p>
<pre class="cpp">
Employee() { d <span class="operator">=</span> <span class="keyword">new</span> EmployeeData; }
Employee(<span class="type">int</span> id<span class="operator">,</span> <span class="keyword">const</span> <span class="type"><a href="qstring.html">QString</a></span> <span class="operator">&</span>name) {
d <span class="operator">=</span> <span class="keyword">new</span> EmployeeData;
setId(id);
setName(name);
}
</pre>
<p>Note that class <code>Employee</code> also has a trivial copy constructor defined, which is not strictly required in this case.</p>
<pre class="cpp">
Employee(<span class="keyword">const</span> Employee <span class="operator">&</span>other)
: d (other<span class="operator">.</span>d)
{
}
</pre>
<p>The copy constructor is not strictly required here, because class <code>EmployeeData</code> is included in the same file as class <code>Employee</code> (<code>employee.h</code>). However, including the private subclass of <a href="qshareddata.html">QSharedData</a> in the same file as the public class containing the <a href="qshareddatapointer.html">QSharedDataPointer</a> is not typical. Normally, the idea is to hide the private subclass of <a href="qshareddata.html">QSharedData</a> from the user by putting it in a separate file which would not be included in the public file. In this case, we would normally put class <code>EmployeeData</code> in a separate file, which would <i>not</i> be included in <code>employee.h</code>. Instead, we would just predeclare the private subclass <code>EmployeeData</code> in <code>employee.h</code> this way:</p>
<pre class="cpp">
<span class="keyword">class</span> EmployeeData;
</pre>
<p>If we had done it that way here, the copy constructor shown would be required. Since the copy constructor is trivial, you might as well just always include it.</p>
<p>Behind the scenes, <a href="qshareddatapointer.html">QSharedDataPointer</a> automatically increments the reference count whenever an <code>Employee</code> object is copied, assigned, or passed as a parameter. It decrements the reference count whenever an <code>Employee</code> object is deleted or goes out of scope. The shared <code>EmployeeData</code> object is deleted automatically if and when the reference count reaches 0.</p>
<p>In a non-const member function of <code>Employee</code>, whenever the <i>d pointer</i> is dereferenced, <a href="qshareddatapointer.html">QSharedDataPointer</a> automatically calls <a href="qshareddatapointer.html#detach">detach</a>() to ensure that the function operates on its own copy of the data.</p>
<pre class="cpp">
<span class="type">void</span> setId(<span class="type">int</span> id) { d<span class="operator">-</span><span class="operator">></span>id <span class="operator">=</span> id; }
<span class="type">void</span> setName(<span class="keyword">const</span> <span class="type"><a href="qstring.html">QString</a></span> <span class="operator">&</span>name) { d<span class="operator">-</span><span class="operator">></span>name <span class="operator">=</span> name; }
</pre>
<p>Note that if <a href="qshareddatapointer.html#detach">detach</a>() is called more than once in a member function due to multiple dereferences of the <i>d pointer</i>, <a href="qshareddatapointer.html#detach">detach</a>() will only create a copy of the shared data the first time it is called, if at all, because on the second and subsequent calls of <a href="qshareddatapointer.html#detach">detach</a>(), the reference count will be 1 again.</p>
<p>But note that in the second <code>Employee</code> constructor, which takes an employee ID and a name, both setId() and setName() are called, but they don't cause <i>copy on write</i>, because the reference count for the newly constructed <code>EmployeeData</code> object has just been set to 1.</p>
<p>In <code>Employee</code>'s <i>const</i> member functions, dereferencing the <i>d pointer</i> does <i>not</i> cause <a href="qshareddatapointer.html#detach">detach</a>() to be called.</p>
<pre class="cpp">
<span class="type">int</span> id() <span class="keyword">const</span> { <span class="keyword">return</span> d<span class="operator">-</span><span class="operator">></span>id; }
<span class="type"><a href="qstring.html">QString</a></span> name() <span class="keyword">const</span> { <span class="keyword">return</span> d<span class="operator">-</span><span class="operator">></span>name; }
</pre>
<p>Notice that there is no need to implement a copy constructor or an assignment operator for the <code>Employee</code> class, because the copy constructor and assignment operator provided by the C++ compiler will do the <i>member by member</i> shallow copy required. The only member to copy is the <i>d pointer</i>, which is a <a href="qshareddatapointer.html">QSharedDataPointer</a>, whose <code>operator=()</code> just increments the reference count of the shared <code>EmployeeData</code> object.</p>
<a name="implicit-vs-explicit-sharing"></a><a name="implicit-vs-explicit-sharing"></a>
<h3 >Implicit vs Explicit Sharing</h3>
<p>Implicit sharing might not be right for the <code>Employee</code> class. Consider a simple example that creates two instances of the implicitly shared <code>Employee</code> class.</p>
<pre class="cpp">
<span class="preprocessor">#include "employee.h"</span>
<span class="type">int</span> main()
{
Employee e1(<span class="number">1001</span><span class="operator">,</span> <span class="string">"Albrecht Durer"</span>);
Employee e2 <span class="operator">=</span> e1;
e1<span class="operator">.</span>setName(<span class="string">"Hans Holbein"</span>);
}
</pre>
<p>After the second employee e2 is created and e1 is assigned to it, both <code>e1</code> and <code>e2</code> refer to Albrecht Durer, employee 1001. Both <code>Employee</code> objects point to the same instance of <code>EmployeeData</code>, which has reference count 2. Then <code>e1.setName("Hans Holbein")</code> is called to change the employee name, but because the reference count is greater than 1, a <i>copy on write</i> is performed before the name is changed. Now <code>e1</code> and <code>e2</code> point to different <code>EmployeeData</code> objects. They have different names, but both have ID 1001, which is probably not what you want. You can, of course, just continue with <code>e1.setId(1002)</code>, if you really mean to create a second, unique employee, but if you only want to change the employee's name everywhere, consider using <a href="qexplicitlyshareddatapointer.html">explicit sharing</a> in the <code>Employee</code> class instead of implicit sharing.</p>
<p>If you declare the <i>d pointer</i> in the <code>Employee</code> class to be <code>QExplicitlySharedDataPointer<EmployeeData></code>, then explicit sharing is used and <i>copy on write</i> operations are not performed automatically (i.e. <a href="qshareddatapointer.html#detach">detach</a>() is not called in non-const functions). In that case, after <code>e1.setName("Hans Holbein")</code>, the employee's name has been changed, but both e1 and e2 still refer to the same instance of <code>EmployeeData</code>, so there is only one employee with ID 1001.</p>
<p>In the member function documentation, <i>d pointer</i> always refers to the internal pointer to the shared data object.</p>
<a name="optimize-performance-for-usage-in-qt-containers"></a>
<h3 >Optimize Performance for Usage in Qt Containers</h3>
<p>You should consider marking your implicitly shared class as a movable type using the <a href="qtglobal.html#Q_DECLARE_TYPEINFO">Q_DECLARE_TYPEINFO</a>() macro if it resembles the <code>Employee</code> class above and uses a <a href="qshareddatapointer.html">QSharedDataPointer</a> or <a href="qexplicitlyshareddatapointer.html">QExplicitlySharedDataPointer</a> as the only member. This can improve performance and memory efficiency when using Qt's <a href="containers.html">container classes</a>.</p>
</div>
<p><b>See also </b><a href="qshareddata.html">QSharedData</a>, <a href="qexplicitlyshareddatapointer.html">QExplicitlySharedDataPointer</a>, <a href="qscopedpointer.html">QScopedPointer</a>, and <a href="qsharedpointer.html">QSharedPointer</a>.</p>
<!-- @@@QSharedDataPointer -->
<div class="types">
<h2>Member Type Documentation</h2>
<!-- $$$Type -->
<h3 class="fn" id="Type-typedef"><a name="Type-typedef"></a>typedef QSharedDataPointer::<span class="name">Type</span></h3>
<p>This is the type of the shared data object. The <i>d pointer</i> points to an object of this type.</p>
<!-- @@@Type -->
</div>
<div class="func">
<h2>Member Function Documentation</h2>
<!-- $$$QSharedDataPointer[overload1]$$$QSharedDataPointer -->
<h3 class="fn" id="QSharedDataPointer"><a name="QSharedDataPointer"></a>QSharedDataPointer::<span class="name">QSharedDataPointer</span>()</h3>
<p>Constructs a <a href="qshareddatapointer.html">QSharedDataPointer</a> initialized with a null <i>d pointer</i>.</p>
<!-- @@@QSharedDataPointer -->
<!-- $$$QSharedDataPointer$$$QSharedDataPointerT* -->
<h3 class="fn" id="QSharedDataPointer-1"><a name="QSharedDataPointer-1"></a>QSharedDataPointer::<span class="name">QSharedDataPointer</span>(<span class="type">T</span> *<i>sharedData</i>)</h3>
<p>Constructs a <a href="qshareddatapointer.html">QSharedDataPointer</a> with <i>d pointer</i> set to <i>sharedData</i> and increments <i>sharedData</i>'s reference count.</p>
<!-- @@@QSharedDataPointer -->
<!-- $$$QSharedDataPointer$$$QSharedDataPointerconstQSharedDataPointer<T>& -->
<h3 class="fn" id="QSharedDataPointer-2"><a name="QSharedDataPointer-2"></a>QSharedDataPointer::<span class="name">QSharedDataPointer</span>(const <span class="type"><a href="qshareddatapointer.html#QSharedDataPointer">QSharedDataPointer</a></span><<span class="type">T</span>> &<i>other</i>)</h3>
<p>Sets the <i>d pointer</i> of <i>this</i> to the <i>d pointer</i> in <i>other</i> and increments the reference count of the shared data object.</p>
<!-- @@@QSharedDataPointer -->
<!-- $$$QSharedDataPointer$$$QSharedDataPointerQSharedDataPointer&& -->
<h3 class="fn" id="QSharedDataPointer-3"><a name="QSharedDataPointer-3"></a>QSharedDataPointer::<span class="name">QSharedDataPointer</span>(<span class="type"><a href="qshareddatapointer.html#QSharedDataPointer">QSharedDataPointer</a></span> &&<i>o</i>)</h3>
<p>Move-constructs a <a href="qshareddatapointer.html">QSharedDataPointer</a> instance, making it point at the same object that <i>o</i> was pointing to.</p>
<p>This function was introduced in Qt 5.2.</p>
<!-- @@@QSharedDataPointer -->
<!-- $$$~QSharedDataPointer[overload1]$$$~QSharedDataPointer -->
<h3 class="fn" id="dtor.QSharedDataPointer"><a name="dtor.QSharedDataPointer"></a>QSharedDataPointer::<span class="name">~QSharedDataPointer</span>()</h3>
<p>Decrements the reference count of the shared data object. If the reference count becomes 0, the shared data object is deleted. <i>This</i> is then destroyed.</p>
<!-- @@@~QSharedDataPointer -->
<!-- $$$clone[overload1]$$$clone -->
<h3 class="fn" id="clone"><a name="clone"></a><code>[protected] </code><span class="type">T</span> *QSharedDataPointer::<span class="name">clone</span>()</h3>
<p>Creates and returns a deep copy of the current data. This function is called by <a href="qshareddatapointer.html#detach">detach</a>() when the reference count is greater than 1 in order to create the new copy. This function uses the <i>operator new</i> and calls the copy constructor of the type T.</p>
<p>This function is provided so that you may support "virtual copy constructors" for your own types. In order to so, you should declare a template-specialization of this function for your own type, like the example below:</p>
<pre class="cpp">
<span class="keyword">template</span><span class="operator"><</span><span class="operator">></span>
EmployeeData <span class="operator">*</span><span class="type"><a href="qshareddatapointer.html#QSharedDataPointer">QSharedDataPointer</a></span><span class="operator"><</span>EmployeeData<span class="operator">></span><span class="operator">::</span>clone()
{
<span class="keyword">return</span> d<span class="operator">-</span><span class="operator">></span>clone();
}
</pre>
<p>In the example above, the template specialization for the clone() function calls the <i>EmployeeData::clone()</i> virtual function. A class derived from EmployeeData could override that function and return the proper polymorphic type.</p>
<p>This function was introduced in Qt 4.5.</p>
<!-- @@@clone -->
<!-- $$$constData[overload1]$$$constData -->
<h3 class="fn" id="constData"><a name="constData"></a>const <span class="type">T</span> *QSharedDataPointer::<span class="name">constData</span>() const</h3>
<p>Returns a const pointer to the shared data object. This function does <i>not</i> call <a href="qshareddatapointer.html#detach">detach</a>().</p>
<p><b>See also </b><a href="qshareddatapointer.html#data">data</a>().</p>
<!-- @@@constData -->
<!-- $$$data[overload1]$$$data -->
<h3 class="fn" id="data"><a name="data"></a><span class="type">T</span> *QSharedDataPointer::<span class="name">data</span>()</h3>
<p>Returns a pointer to the shared data object. This function calls <a href="qshareddatapointer.html#detach">detach</a>().</p>
<p><b>See also </b><a href="qshareddatapointer.html#constData">constData</a>().</p>
<!-- @@@data -->
<!-- $$$data$$$data -->
<h3 class="fn" id="data-1"><a name="data-1"></a>const <span class="type">T</span> *QSharedDataPointer::<span class="name">data</span>() const</h3>
<p>Returns a pointer to the shared data object. This function does <i>not</i> call <a href="qshareddatapointer.html#detach">detach</a>().</p>
<!-- @@@data -->
<!-- $$$detach[overload1]$$$detach -->
<h3 class="fn" id="detach"><a name="detach"></a><span class="type">void</span> QSharedDataPointer::<span class="name">detach</span>()</h3>
<p>If the shared data object's reference count is greater than 1, this function creates a deep copy of the shared data object and sets the <i>d pointer</i> of <i>this</i> to the copy.</p>
<p>This function is called automatically by non-const member functions of <a href="qshareddatapointer.html">QSharedDataPointer</a> if <i>copy on write</i> is required. You don't need to call it yourself.</p>
<!-- @@@detach -->
<!-- $$$swap[overload1]$$$swapQSharedDataPointer& -->
<h3 class="fn" id="swap"><a name="swap"></a><span class="type">void</span> QSharedDataPointer::<span class="name">swap</span>(<span class="type"><a href="qshareddatapointer.html#QSharedDataPointer">QSharedDataPointer</a></span> &<i>other</i>)</h3>
<p>Swap this instance's shared data pointer with the shared data pointer in <i>other</i>.</p>
<!-- @@@swap -->
<!-- $$$operator T *[overload1]$$$operator T * -->
<h3 class="fn" id="operator-T--2a"><a name="operator-T--2a"></a>QSharedDataPointer::<span class="name">operator T *</span>()</h3>
<p>Returns a pointer to the shared data object. This function calls <a href="qshareddatapointer.html#detach">detach</a>().</p>
<p><b>See also </b><a href="qshareddatapointer.html#data">data</a>() and <a href="qshareddatapointer.html#constData">constData</a>().</p>
<!-- @@@operator T * -->
<!-- $$$operator const T *[overload1]$$$operator const T * -->
<h3 class="fn" id="operator-const-T--2a"><a name="operator-const-T--2a"></a>QSharedDataPointer::<span class="name">operator const T *</span>() const</h3>
<p>Returns a pointer to the shared data object. This function does <i>not</i> call <a href="qshareddatapointer.html#detach">detach</a>().</p>
<!-- @@@operator const T * -->
<!-- $$$operator![overload1]$$$operator! -->
<h3 class="fn" id="operator-not"><a name="operator-not"></a><span class="type">bool</span> QSharedDataPointer::<span class="name">operator!</span>() const</h3>
<p>Returns <code>true</code> if the <i>d pointer</i> of <i>this</i> is null.</p>
<!-- @@@operator! -->
<!-- $$$operator!=[overload1]$$$operator!=constQSharedDataPointer<T>& -->
<h3 class="fn" id="operator-not-eq"><a name="operator-not-eq"></a><span class="type">bool</span> QSharedDataPointer::<span class="name">operator!=</span>(const <span class="type"><a href="qshareddatapointer.html#QSharedDataPointer">QSharedDataPointer</a></span><<span class="type">T</span>> &<i>other</i>) const</h3>
<p>Returns <code>true</code> if <i>other</i> and <i>this</i> do <i>not</i> have the same <i>d pointer</i>. This function does <i>not</i> call <a href="qshareddatapointer.html#detach">detach</a>().</p>
<!-- @@@operator!= -->
<!-- $$$operator*[overload1]$$$operator* -->
<h3 class="fn" id="operator-2a"><a name="operator-2a"></a><span class="type">T</span> &QSharedDataPointer::<span class="name">operator*</span>()</h3>
<p>Provides access to the shared data object's members. This function calls <a href="qshareddatapointer.html#detach">detach</a>().</p>
<!-- @@@operator* -->
<!-- $$$operator*$$$operator* -->
<h3 class="fn" id="operator-2a-1"><a name="operator-2a-1"></a>const <span class="type">T</span> &QSharedDataPointer::<span class="name">operator*</span>() const</h3>
<p>Provides const access to the shared data object's members. This function does <i>not</i> call <a href="qshareddatapointer.html#detach">detach</a>().</p>
<!-- @@@operator* -->
<!-- $$$operator->[overload1]$$$operator-> -->
<h3 class="fn" id="operator--gt"><a name="operator--gt"></a><span class="type">T</span> *QSharedDataPointer::<span class="name">operator-></span>()</h3>
<p>Provides access to the shared data object's members. This function calls <a href="qshareddatapointer.html#detach">detach</a>().</p>
<!-- @@@operator-> -->
<!-- $$$operator->$$$operator-> -->
<h3 class="fn" id="operator--gt-1"><a name="operator--gt-1"></a>const <span class="type">T</span> *QSharedDataPointer::<span class="name">operator-></span>() const</h3>
<p>Provides const access to the shared data object's members. This function does <i>not</i> call <a href="qshareddatapointer.html#detach">detach</a>().</p>
<!-- @@@operator-> -->
<!-- $$$operator=[overload1]$$$operator=constQSharedDataPointer<T>& -->
<h3 class="fn" id="operator-eq"><a name="operator-eq"></a><span class="type"><a href="qshareddatapointer.html#QSharedDataPointer">QSharedDataPointer</a></span><<span class="type">T</span>> &QSharedDataPointer::<span class="name">operator=</span>(const <span class="type"><a href="qshareddatapointer.html#QSharedDataPointer">QSharedDataPointer</a></span><<span class="type">T</span>> &<i>other</i>)</h3>
<p>Sets the <i>d pointer</i> of <i>this</i> to the <i>d pointer</i> of <i>other</i> and increments the reference count of the shared data object. The reference count of the old shared data object of <i>this</i> is decremented. If the reference count of the old shared data object becomes 0, the old shared data object is deleted.</p>
<!-- @@@operator= -->
<!-- $$$operator=$$$operator=T* -->
<h3 class="fn" id="operator-eq-1"><a name="operator-eq-1"></a><span class="type"><a href="qshareddatapointer.html#QSharedDataPointer">QSharedDataPointer</a></span> &QSharedDataPointer::<span class="name">operator=</span>(<span class="type">T</span> *<i>sharedData</i>)</h3>
<p>Sets the <i>d pointer</i> og <i>this</i> to <i>sharedData</i> and increments <i>sharedData</i>'s reference count. The reference count of the old shared data object of <i>this</i> is decremented. If the reference count of the old shared data object becomes 0, the old shared data object is deleted.</p>
<!-- @@@operator= -->
<!-- $$$operator=$$$operator=QSharedDataPointer<T>&& -->
<h3 class="fn" id="operator-eq-2"><a name="operator-eq-2"></a><span class="type"><a href="qshareddatapointer.html#QSharedDataPointer">QSharedDataPointer</a></span><<span class="type">T</span>> &QSharedDataPointer::<span class="name">operator=</span>(<span class="type"><a href="qshareddatapointer.html#QSharedDataPointer">QSharedDataPointer</a></span><<span class="type">T</span>> &&<i>other</i>)</h3>
<p>Move-assigns <i>other</i> to this <a href="qshareddatapointer.html">QSharedDataPointer</a> instance.</p>
<p>This function was introduced in Qt 5.2.</p>
<!-- @@@operator= -->
<!-- $$$operator==[overload1]$$$operator==constQSharedDataPointer<T>& -->
<h3 class="fn" id="operator-eq-eq"><a name="operator-eq-eq"></a><span class="type">bool</span> QSharedDataPointer::<span class="name">operator==</span>(const <span class="type"><a href="qshareddatapointer.html#QSharedDataPointer">QSharedDataPointer</a></span><<span class="type">T</span>> &<i>other</i>) const</h3>
<p>Returns <code>true</code> if <i>other</i> and <i>this</i> have the same <i>d pointer</i>. This function does <i>not</i> call <a href="qshareddatapointer.html#detach">detach</a>().</p>
<!-- @@@operator== -->
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