Question

struct BaseType
{
    int x1;
    float x2;
};

struct ChildType
{
    int y1;
    float y2;
};

Class Base       
{             
    BaseType  obj;           

    void funcBase(BaseType **ptr)
    {

        *ptr = &obj;                   // When this assignment happens ofcourse obj is of the BaseType as the  LHS ptr is pointing to a BaseType                                            

  Now I want to write a C++ equivalent code of the following 2 algorithmic statements,                                       

        BaseType's obj.x1 = ChildTypes's obj.y1;                       
        BaseType's obj.x2 = ChildTypes's.obj.y1;                  


    }               
};

class Child :: public Base
{
    ChildType obj;  

};   

I wnat to access child’s obj.y1 from base and assign it to base’s obj.x1.

But 1 thing to remember that object name in base and child is same
“obj”.

Can anyone kindly help me in this. Thanks.

Answer 1

Your question is somewhat vague, but from what I can gather, you want something like this:

ChildType* child = dynamic_cast<ChildType*>( &obj );

Now child is pointing to obj, as if it were of type ChildType, assuming the cast is successful.

Read more about typecasting here.

EDIT: I should just mention that typecasting like this should be avoided if a better design can substitute it. Perhaps you should reconsider your overall design for a moment here.

EDIT2: Given your recent edit, here’s a more specific block of example code:

ChildType* child = dynamic_cast<ChildType*>( &obj );
obj.x1 = child->y1;
obj.x2 = child->y2;