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POPolymorphism and inheritance of static members in C++
 

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    <p>I need to keep a list(vector) of children for every class, and I've got a tricky problem:</p> <pre><code>class A { protected: int a; static vector&lt;A*&gt; children; public: A(int a): a(a) {;}; virtual void AddToChildren(A* obj); virtual void ShowChildren(); virtual void Show(); }; class B: public A { protected: int b; static vector&lt;A*&gt; children; public: B(int a, int b): b(b), A(a) { A::AddToChildren(this);}; virtual void Show(); }; class C: public B { protected: int c; public: C(int a, int b, int c): c(c), B(a,b) { B::AddToChildren(this);}; virtual void Show(); }; vector&lt;A*&gt; A::children=vector&lt;A*&gt;(); vector&lt;A*&gt; B::children=vector&lt;A*&gt;(); void A::AddToChildren(A *obj) { children.push_back(obj); } void A::ShowChildren() { for(vector&lt;A*&gt;::iterator i=children.begin(); i!=children.end();i++) (*i)-&gt;Show(); } </code></pre> <p>Adding A(0), B(1,1) and C(2,2,2) and calling a.ShowChildren gives: 1,1 ; 2,2,2 ; 2,2,2</p> <p>Every time I make an instance of class C the A::children is updated instead of B::children and A::children. Sooo... the class C is added twice to the children of A class, but not added to class B. It helps when I copy the AddChildren class (<em>literally</em> copy) to class B, so that every class has its own AddChildren/ShowChildren. Also I've managed to accomplish this task using pointers, but I'm wondering is there a better way. I think that the problem is somewhere in the "using the right vector", but I don't know how to force the compiler to use the right one. </p> <p>I would be grateful for any suggestions on whatever I'm doing wrong here. </p> <p>First of all, thank you all for your comments and help. Using your advice (about my design and virtual GetList()) I managed to simplify my program:</p> <pre><code>class A { protected: int a; virtual vector&lt;A*&gt;* GetList(); public: A(int a): a(a) {;}; A(int a, A* inherited):a(a) { AddToChildren(inherited);}; static vector&lt;A*&gt; children; virtual void AddToChildren(A* obj); virtual void ShowChildren(); virtual void Show(); }; class B: public A { protected: int b; virtual vector&lt;A*&gt;* GetList(); public: static vector&lt;A*&gt; children; B(int a, int b): b(b), A(a,this){;}; B(int a, int b, A* inherited) : b(b), A(a,this){AddToChildren(inherited);}; virtual void Show(); }; class C: public B { protected: int c; public: C(int a, int b, int c): c(c), B(a,b,this) { }; virtual void Show(); virtual vector&lt;A*&gt;* GetList(); }; vector&lt;A*&gt; A::children=vector&lt;A*&gt;(); vector&lt;A*&gt; B::children=vector&lt;A*&gt;(); void A::AddToChildren(A *obj) { GetList()-&gt;push_back(obj); } void A::ShowChildren() { for(vector&lt;A*&gt;::iterator i=GetList()-&gt;begin(); i!=GetList()-&gt;end();i++) (*i)-&gt;Show(); } vector&lt;A*&gt; * A::GetList() { return &amp; children; } vector&lt;A*&gt; * B::GetList() { return &amp; children; } vector&lt;A*&gt; * C::GetList() { return &amp; children; } </code></pre> <p>Now its using constructors without calling the upper class, it just calls the proper constructor of the upper class. Its not the best, but i think it's better. </p> <p>Once more, thank you all for help. </p>
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