Question

Is it possible to initialize objects of one class in the constructor of another class in c++? I usually will declare objects only in the main(), however I am curious to know if this is possible and a good practice. What are the implications with “new” and a case without “new” operator. Where does it get destroyed?

e.g. Assuming one namespace and an example with “new” operator

class A{
private:
protected:
int *w, int *h;
public:
A(){
 w = new int;
 h = new int;
 };
virtual int area (return ((*w)*(*h)) ;)
virtual ~A()
 {
  delete w;
  delete h;
 }
}

class B{
public:
B()
{
 A a1; // This is usually in the main();
 // Is this good practice
 //Where will the object be destroyed
}
virtual ~B();
}

Answer 1

About your actual question, yes this is perfectly good practice (as far as declaring A inside B’s constructor goes). This will work and properly call A’s destructor.

However: About the code snippet you posted, allocating two objects in A’s constructor is not good practice. If operator new for h fails, then w will be leaked. A’s destructor will not be called if an exception is thrown inside its constructor. Thus, w will not be deleted if new int throws for h.