Re: calling a pure virtual from base constructor
christian.bongiorno@gmail.com wrote:
I am trying to call a pure virtual function from the constructor of an
bastract BaseClass
However, I get a linker error: unresolved symbol. The pure virtual is
defined in the grandparent, the parent invokes the virtual from the
constructor, the child implements it:
class GrandParent {
virtual getClass() = 0;
};
class Parent : public GrandParent {
Parent() { getClass();}
};
class Child : public Parent {
int getClass() { return 10;}
}
How can I do this? I guess I can pass the value in the constructor, but
that's not what I want to do
The problem is that the order of constructors is first parent, then
child. When the parent constructor is called, the child object doesn't
exist. The standard solution is to define the 'Init' virtual method and
call it after the object is constructed.
Another solution is to define an inheriting class for initialization.
// initializes the object with getClass
template<typename T>
class GetClass: public T
{
GetClass() { getClass();}
};
Remove the Parent class, and now for every Child class that inherits
from CrandParent, you can USE the GetClass<Child> class instead.
Michael
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