Changed Lazy<T> to take a lambda-function in its constructor. This avoids the need for sub-classing.

docs/d0/dce/class_m_utils_1_1_lazy.html

@@ -65,10 +65,9 @@ $(function() {
 <div class="header">
   <div class="summary">
 <a href="#pub-methods">Public Member Functions</a> &#124;
-<a href="#pro-methods">Protected Member Functions</a> &#124;
 <a href="../../da/d44/class_m_utils_1_1_lazy-members.html">List of all members</a>  </div>
   <div class="headertitle">
-<div class="title">MUtils::Lazy&lt; T &gt; Class Template Reference<span class="mlabels"><span class="mlabel">abstract</span></span></div>  </div>
+<div class="title">MUtils::Lazy&lt; T &gt; Class Template Reference</div>  </div>
 </div><!--header-->
 <div class="contents">
 
@@ -79,23 +78,20 @@ $(function() {
 <table class="memberdecls">
 <tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="pub-methods"></a>
 Public Member Functions</h2></td></tr>
+<tr class="memitem:a7dc7baa7d7ac31c644965be2ccc4d8cd"><td class="memItemLeft" align="right" valign="top"><a id="a7dc7baa7d7ac31c644965be2ccc4d8cd"></a>
+&#160;</td><td class="memItemRight" valign="bottom"><b>Lazy</b> (std::function&lt; T *(void)&gt; &amp;&amp;initializer)</td></tr>
+<tr class="separator:a7dc7baa7d7ac31c644965be2ccc4d8cd"><td class="memSeparator" colspan="2">&#160;</td></tr>
 <tr class="memitem:a86cf7d344a38ea09d37d27acd8993f45"><td class="memItemLeft" align="right" valign="top"><a id="a86cf7d344a38ea09d37d27acd8993f45"></a>
 T &amp;&#160;</td><td class="memItemRight" valign="bottom"><b>operator*</b> (void)</td></tr>
 <tr class="separator:a86cf7d344a38ea09d37d27acd8993f45"><td class="memSeparator" colspan="2">&#160;</td></tr>
-</table><table class="memberdecls">
-<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="pro-methods"></a>
-Protected Member Functions</h2></td></tr>
-<tr class="memitem:a03f52adf0e421b20298f2f7578e3375f"><td class="memItemLeft" align="right" valign="top"><a id="a03f52adf0e421b20298f2f7578e3375f"></a>
-virtual T *&#160;</td><td class="memItemRight" valign="bottom"><b>create</b> ()=0</td></tr>
-<tr class="separator:a03f52adf0e421b20298f2f7578e3375f"><td class="memSeparator" colspan="2">&#160;</td></tr>
 </table>
 <a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
 <div class="textblock"><h3>template&lt;typename T&gt;<br />
 class MUtils::Lazy&lt; T &gt;</h3>
 
 <p><a class="el" href="../../d0/dce/class_m_utils_1_1_lazy.html" title="Lazy initialization template class. ">Lazy</a> initialization template class. </p>
-<p>In order to create your own "lazy" initializer, inherit from the <code><a class="el" href="../../d0/dce/class_m_utils_1_1_lazy.html" title="Lazy initialization template class. ">Lazy</a>&lt;T&gt;</code> class an implement the <a class="el" href="../../d2/dad/_hash_8h.html#a330b73d6927d6cd95892712f9396f40e" title="Create instance of a hash function. ">create()</a> function. The lazy-initialized value can be obtained from a <code><a class="el" href="../../d0/dce/class_m_utils_1_1_lazy.html" title="Lazy initialization template class. ">Lazy</a>&lt;T&gt;</code> instance by using the <code>operator*()</code>. Initialization of the value happens when the <code>operator*()</code> is called for the very first time, by invoking the concrete <a class="el" href="../../d2/dad/_hash_8h.html#a330b73d6927d6cd95892712f9396f40e" title="Create instance of a hash function. ">create()</a> function. The return value of <a class="el" href="../../d2/dad/_hash_8h.html#a330b73d6927d6cd95892712f9396f40e" title="Create instance of a hash function. ">create()</a> is then stored internally, so that any subsequent call to the <code>operator*()</code> immediately returns the previously created value.</p>
-<p><b>Note on thread-saftey:</b> This class is thread-safe in the sense that all calls to <code>operator*()</code> on the same <code><a class="el" href="../../d0/dce/class_m_utils_1_1_lazy.html" title="Lazy initialization template class. ">Lazy</a>&lt;T&gt;</code> instance, regardless from which thread, are guaranteed to return the exactly same value/object. Still, if the value has <em>not</em> been initialized yet <b>and</b> if multiple threads happen to call <code>operator*()</code> at the same time, then the concrete <a class="el" href="../../d2/dad/_hash_8h.html#a330b73d6927d6cd95892712f9396f40e" title="Create instance of a hash function. ">create()</a> function <em>may</em> be invoked more than once (concurrently and by different threads). In that case, all but one return value of <a class="el" href="../../d2/dad/_hash_8h.html#a330b73d6927d6cd95892712f9396f40e" title="Create instance of a hash function. ">create()</a> are discarded, and all threads eventually receive the same value/object. </p>
+<p>The lazy-initialized value of type T can be obtained from a <code><a class="el" href="../../d0/dce/class_m_utils_1_1_lazy.html" title="Lazy initialization template class. ">Lazy</a>&lt;T&gt;</code> instance by using the <code>operator*()</code>. Initialization of the value happens when the <code>operator*()</code> is called for the very first time, by invoking the <code>initializer</code> lambda-function that was passed to the constructor. The return value of the <code>initializer</code> lambda-function is then stored internally, so that any subsequent call to the <code>operator*()</code> <em>immediately</em> returns the previously created value.</p>
+<p><b>Note on thread-saftey:</b> This class is thread-safe in the sense that all calls to <code>operator*()</code> on the same <code><a class="el" href="../../d0/dce/class_m_utils_1_1_lazy.html" title="Lazy initialization template class. ">Lazy</a>&lt;T&gt;</code> instance, regardless from which thread, are guaranteed to return the exactly same value/object. Still, if the value has <em>not</em> been initialized yet <b>and</b> if multiple threads happen to call <code>operator*()</code> at the same time, then the <code>initializer</code> lambda-function <em>may</em> be invoked more than once (concurrently and by different threads). In that case, all but one return value of the <code>initializer</code> lambda-function are discarded, and all threads eventually obtain the same value/object. </p>
 </div><hr/>The documentation for this class was generated from the following file:<ul>
 <li>include/MUtils/<a class="el" href="../../d8/d4d/_lazy_8h_source.html">Lazy.h</a></li>
 </ul>

docs/d8/d4d/_lazy_8h.html

@@ -75,8 +75,8 @@ $(function() {
 <a href="#details">More...</a></p>
 <div class="textblock"><code>#include &lt;<a class="el" href="../../d5/d3b/_global_8h_source.html">MUtils/Global.h</a>&gt;</code><br />
 <code>#include &lt;MUtils/Exception.h&gt;</code><br />
-<code>#include &lt;QScopedPointer&gt;</code><br />
 <code>#include &lt;QAtomicPointer&gt;</code><br />
+<code>#include &lt;functional&gt;</code><br />
 </div>
 <p><a href="../../d8/d4d/_lazy_8h_source.html">Go to the source code of this file.</a></p>
 <table class="memberdecls">

docs/da/d44/class_m_utils_1_1_lazy-members.html

@@ -70,7 +70,7 @@ $(function() {
 
 <p>This is the complete list of members for <a class="el" href="../../d0/dce/class_m_utils_1_1_lazy.html">MUtils::Lazy&lt; T &gt;</a>, including all inherited members.</p>
 <table class="directory">
-  <tr bgcolor="#f0f0f0" class="even"><td class="entry"><b>create</b>()=0 (defined in <a class="el" href="../../d0/dce/class_m_utils_1_1_lazy.html">MUtils::Lazy&lt; T &gt;</a>)</td><td class="entry"><a class="el" href="../../d0/dce/class_m_utils_1_1_lazy.html">MUtils::Lazy&lt; T &gt;</a></td><td class="entry"><span class="mlabel">protected</span><span class="mlabel">pure virtual</span></td></tr>
+  <tr bgcolor="#f0f0f0" class="even"><td class="entry"><b>Lazy</b>(std::function&lt; T *(void)&gt; &amp;&amp;initializer) (defined in <a class="el" href="../../d0/dce/class_m_utils_1_1_lazy.html">MUtils::Lazy&lt; T &gt;</a>)</td><td class="entry"><a class="el" href="../../d0/dce/class_m_utils_1_1_lazy.html">MUtils::Lazy&lt; T &gt;</a></td><td class="entry"><span class="mlabel">inline</span></td></tr>
   <tr bgcolor="#f0f0f0"><td class="entry"><b>operator*</b>(void) (defined in <a class="el" href="../../d0/dce/class_m_utils_1_1_lazy.html">MUtils::Lazy&lt; T &gt;</a>)</td><td class="entry"><a class="el" href="../../d0/dce/class_m_utils_1_1_lazy.html">MUtils::Lazy&lt; T &gt;</a></td><td class="entry"><span class="mlabel">inline</span></td></tr>
 </table></div><!-- contents -->
 <!-- start footer part -->

include/MUtils/Lazy.h

@@ -31,44 +31,46 @@
 #include <MUtils/Exception.h>
 
 //Qt
-#include <QScopedPointer>
 #include <QAtomicPointer>
 
+//CRT
+#include <functional>
+
 namespace MUtils
 {
 	/**
 	* \brief Lazy initialization template class
 	*
-	* In order to create your own "lazy" initializer, inherit from the `Lazy<T>` class an implement the create() function. The lazy-initialized value can be obtained from a `Lazy<T>` instance by using the `operator*()`. Initialization of the value happens when the `operator*()` is called for the very first time, by invoking the concrete create() function. The return value of create() is then stored internally, so that any subsequent call to the `operator*()` immediately returns the previously created value.
+	* The lazy-initialized value of type T can be obtained from a `Lazy<T>` instance by using the `operator*()`. Initialization of the value happens when the `operator*()` is called for the very first time, by invoking the `initializer` lambda-function that was passed to the constructor. The return value of the `initializer` lambda-function is then stored internally, so that any subsequent call to the `operator*()` *immediately* returns the previously created value.
 	*
-	* **Note on thread-saftey:** This class is thread-safe in the sense that all calls to `operator*()` on the same `Lazy<T>` instance, regardless from which thread, are guaranteed to return the exactly same value/object. Still, if the value has *not* been initialized yet **and** if multiple threads happen to call `operator*()` at the same time, then the concrete create() function *may* be invoked more than once (concurrently and by different threads). In that case, all but one return value of create() are discarded, and all threads eventually receive the same value/object.
+	* **Note on thread-saftey:** This class is thread-safe in the sense that all calls to `operator*()` on the same `Lazy<T>` instance, regardless from which thread, are guaranteed to return the exactly same value/object. Still, if the value has *not* been initialized yet **and** if multiple threads happen to call `operator*()` at the same time, then the `initializer` lambda-function *may* be invoked more than once (concurrently and by different threads). In that case, all but one return value of the `initializer` lambda-function are discarded, and all threads eventually obtain the same value/object.
 	*/
 	template<typename T> class Lazy
 	{
 	public:
+		Lazy(std::function<T*(void)> &&initializer) : m_initializer(initializer) { }
+
 		T& operator*(void)
 		{
-			while (!m_data)
+			while (!m_value)
 			{
-				if (T *const initializer = create())
+				if (T *const value = m_initializer())
 				{
-					if (!m_data.testAndSetOrdered(NULL, initializer))
+					if (!m_value.testAndSetOrdered(NULL, value))
 					{
-						delete initializer;
+						delete value; /*too late*/
 					}
 				}
 				else
 				{
-					MUTILS_THROW("Initializer function returned NULL!");
+					MUTILS_THROW("Initializer returned NULL!");
 				}
 			}
-			return *m_data;
+			return *m_value;
 		}
 
-	protected:
-		virtual T *create() = 0;
-
 	private:
-		QAtomicPointer<T> m_data;
+		QAtomicPointer<T> m_value;
+		const std::function<T*(void)> m_initializer;
 	};
 }