Scope of object variable in classes

[luperkal]

I'm fundamentally confused about this. Can someone please explain it to me clearly?

Say I have two classes A and B. I want to create an object from Class B in class A, and I want to be able to access and work with this object in all of the functions in class A. Do I create the object in the public/private data section of Class B? Do I declare the object in class B's constructor? What exactly do both of those things do? Does it effect the variables scope if I allocate it dynamically with 'new?' I don't want to use 'new' if I don't have to.

[Girish Kanakagiri]

Here The Basic thing is Once you create an Object of Class B, Inside class A.
That object becomes a Data member of Class A and thus; just by creating
an Object of Class A, you can utilise the features of both the classes.

This is called Composition ( One of the Famous Pattern among
the Three which are Aggregation, Association and Composition )

I'm fundamentally confused about this. Can someone please explain it to me clearly?

Say I have two classes A and B. I want to create an object from Class B in class A, and I want to be able to access and work with this object in all of the functions in class A. Do I create the object in the public/private data section of Class B? Do I declare the object in class B's constructor? What exactly do both of those things do? Does it effect the variables scope if I allocate it dynamically with 'new?' I don't want to use 'new' if I don't have to.

[weaknessforcats]

You have not identified the complete relationship between Class A and Class B.

If the object of Class B is to change independently from the object of Class A, then you have an Association and Class A should contain a handle or reference to the Class B object.

If the Class B object is really part of the Class A object, then you have Composition and the Class B object becomes a private member variable of Class A.

If the Class B methods are to be part of the Class A interface, then you publicly derive Class A from Class B provided Class A IS-A kind of Class B. Otherwise, you have Composition and and object of Class B is a private data member in Class A and you write wrapper methods in Class A for the Class B methods. Here, and alternative to the Class A wrapper functions is to have Class A inherit privately from Class B.