Frank Winter wrote: > Nobody would want to write this. But somebody might want to use objects > with virtual functions and define hers object on the stack, like: > > vector<A> ve; > ve.push_back(A()); > ve.push_back(B()); > ve.push_back(A()); > > iterate over it and call ::f(). Then always A::f() gets called, because > its a vector of A. But a B is also an A. Thatfor I can insert it into > the vector. That's not quite correct here; you are not inserting a B into the vector at all. In the second call to push_back(), a temporary B object is instantiated on the stack, and then A's copy constructor is called to create an A from it in the space allocated inside the vector (then the temporary B object is destroyed). The vector does *not* contain a B object at any time. As has previously been mentioned, the only way to use polymorphism with objects in containers is to use pointer-to-object or reference-to-object semantics; if you use value semantics, then the objects will be sliced to the type that the container is defined to hold. -- Kevin P. Fleming Digium, Inc. | Director of Software Technologies 445 Jan Davis Drive NW - Huntsville, AL 35806 - USA skype: kpfleming | jabber: kpfleming@xxxxxxxxxx Check us out at www.digium.com & www.asterisk.org
