C++ inheritance
Author
hello,
i am having a problem with inheritance in C++.
i have a class "node" that defines a virtual function render().
now other classes that extend from node overwrite this render-function.
after that i put all instance of any of those classes in a list and call the render-function.
now i expect that the corresponding render-function in the subclass is being called, but unfortunately the render-function from the baseclass "node" is always called.
let me know if i should provide some code to illustrate the problem.
thanks!
Does your list store nodes by value? If so, then you probably have a slicing issue; only the base part of the objects are being copied into your list. Try using a list of (smart) pointers.
Hm. Thats not right. Something must be going wrong somewhere. A little code wouldn't hurt ;-)
Author
thank you here is the code
node * node1 = new node();node * node2 = new cat();node * tpu = new powerup();tlist->push_back(node1);tlist->push_back(node2);tlist->push_back(tpu);list<node>::iterator theIterator;for( theIterator = tlist.begin(); theIterator != tlist.end(); theIterator++ ) { theIterator->render();}
Ah. So SiCrane was right, only it is a little trickier. Your iterator is splicing the information into a node, try:
I think that will work.
list<node*>::iterator theIterator;for( theIterator = tlist.begin(); theIterator != tlist.end(); theIterator++ ) { (*theIterator)->render();}I think that will work.
Quote:Original post by ehmdjii
thank you here is the code
*** Source Snippet Removed ***
No, it isn't. First of all, you can't be treating 'tlist' as a pointer in some places (the push_back calls) and as a list directly in others (when you create the iterators), and second, you can't put node*'s into a list of node's. Try again.
Author
ok, i was doing some shortcuts, when typing in the code.
here is the actual code
and the scenegraph class
thanks!
here is the actual code
tnode * node1 = new tnode(); tnode * node2 = new tnode(); tnode * tpu = new tpowerup(); tscenegraph * sg = new tscenegraph(); sg->add(node1); sg->add(node2); sg->add(tpu); sg->render();and the scenegraph class
tscenegraph::tscenegraph(void){ nodes = new vector<tnode>();}tscenegraph::~tscenegraph(void){}void tscenegraph::add(tnode * node) { nodes->push_back( *node );}void tscenegraph::render(void){ vector<tnode>::iterator theIterator; for( theIterator = nodes->begin(); theIterator != nodes->end(); theIterator++ ) { (*theIterator).render(); } }thanks!
Your code is a pointer to vector, not a vector of pointers [grin]. Lesson: when you have the code in front of you, it is a crime not to post it.
tnode * node1 = new tnode();tnode * node2 = new tnode();tnode * tpu = new tpowerup();tscenegraph * sg = new tscenegraph();sg->add(node1);sg->add(node2);sg->add(tpu);sg->render();class tscenegraph{public: // ...private: vector<tnode *> nodes;};tscenegraph::tscenegraph(){}tscenegraph::~tscenegraph(void){ // clean up the nodes}void tscenegraph::add(tnode * node) { nodes.push_back( node );}void tscenegraph::render(){ vector<tnode*>::iterator theIterator; for( theIterator = nodes.begin(); theIterator != nodes.end(); theIterator++ ) { theIterator->render(); } }This topic is closed to new replies.
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