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POMapped functors to member functions losing scope
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  1. POMapped functors to member functions losing scope
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    copied!<p>I'd like to be able to call some member functions from different classes which all have the same general syntax and base class. Something along the lines of</p> <pre><code>class A: public BaseClass { public: A(); ~A(); int DoFoo(); int DoBar(); int DoBarBar(); }; class B : public BaseClass { public: B(); ~B(); int DoSomething(); int DoSomethingElse(); int DoAnother(); }; </code></pre> <p>Where I could potentially places the member functions from both classes into one map so that I could have something like</p> <pre><code> key value "Option1" *DoFoo() "Option2" *DoSomething() "Option3" *DoFoo() ... ... "Option6" *DoAnother() </code></pre> <p>Where I could call a function to return a value based on what option I chose, regardless of what class the function belongs to.</p> <p>Through some searching, I tried to implement my own mapped set of functors. However, the map retains the address of the functor, but the functions within become null.</p> <p>Here are my functor declarations which store a class object and a function pointer</p> <pre><code> #include &lt;stdio.h&gt; #include &lt;vector&gt; #include &lt;algorithm&gt; #include &lt;map&gt; #include &lt;string&gt; ////////////////////////////////////////////////////////////// //Functor Classes ////////////////////////////////////////////////////////////// class TFunctor { public: virtual void operator()()=0; // call using operator virtual int Call()=0; // call using function }; // derived template class template &lt;class TClass&gt; class TSpecificFunctor : public TFunctor { private: int (TClass::*fpt)(); // pointer to member function TClass* pt2Object; // pointer to object public: // constructor - takes pointer to an object and pointer to a member and stores // them in two private variables TSpecificFunctor(TClass* _pt2Object, int(TClass::*_fpt)()) { pt2Object = _pt2Object; fpt=_fpt; }; // override operator "()" virtual void operator()() { (*pt2Object.*fpt)();}; // execute member function // override function "Call" virtual int Call() {return (*pt2Object.*fpt)();}; // execute member function }; typedef std::map&lt;std::string, TFunctor*&gt; TestMap; ////////////////////////////////////////////////////////////// //Test Classes ////////////////////////////////////////////////////////////// //Base Test class class base { public: base(int length, int width){m_length = length; m_width = width;} virtual ~base(){} int area(){return m_length*m_width;} int m_length; int m_width; }; //Inherited class which contains two functions I would like to point to class inherit:public base { public: inherit(int length, int width, int height); ~inherit(); int volume(){return base::area()*m_height;} int area2(){return m_width*m_height;} int m_height; TestMap m_map; }; </code></pre> <p>where my inherit class constructor looks like:</p> <pre><code>inherit::inherit(int length, int width, int height):base(length, width) { m_height = height; TSpecificFunctor&lt;inherit&gt; funcA(this, &amp;inherit::volume); m_map["a"] = &amp;funcA; TSpecificFunctor&lt;inherit&gt; funcB(this, &amp;inherit::area2); m_map["b"] = &amp;funcB; } </code></pre> <p>Which is where I am mapping two functions into a map. Things still look okay in the above function in terms of memory address and function pointers.</p> <p>I then try to create an instance of inherit in a new class...</p> <pre><code>class overall { public: overall(); ~overall(){} inherit *m_inherit; TestMap m_mapOverall; }; overall::overall() { m_inherit = new inherit(3,4,5); TestMap tempMap = m_inherit-&gt;m_map; int i = 0; } </code></pre> <p>Here when I look at the values of m_inherit->m_map, I notice that the keys are still consistent, however the memory addresses of the functions which I tried to point to have disappeared.</p> <p>I haven't had much experience with functors but from my understanding, it is able to retain states, which I assume means that I can call member functions outside of its class. But I'm starting to think that my member functions disappear because it is out of scope.</p>
 

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