Inheritance in parameters of constructor.

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Base Classes are A, B, C and their respective Child classes are A1, B1, C1.

-> A class constructor uses two parameters. (B and C)

Like, A (B *b, C *c).

-> A1 class constructor uses two parameters B1 and C1 and I also want to call A constructor at the same time with passing argument B and C.

I have implemented it by this way : A1 (B *b, C *c, B1 *b1, C1 *c1) : A(b,c).

-> But the problem here is I have to maintain two copies; Like base b and child b1. Before calling I have to prepare both b and b1 separately.
Is there any better way to implement it?

What I have tried:

Tried :

A (B *b , C *c).

Tried :
A1 (B *b, C *c, B1 *b1, C1 *c1) : A(b,c).

Posted 9-Jul-18 1:37am

Hemal Shah

Updated 9-Jul-18 2:48am

Kornfeld Eliyahu Peter

v4

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Comments

Kornfeld Eliyahu Peter 9-Jul-18 8:26am

All those A, B and C are confusing...
When you are telling that A's constructor has two parameters of type B and C, do you mean of class B and class C mentioned just before?
So b and b1 are two different objects one of type class B and the other of type class B1?

CPallini 9-Jul-18 8:27am

Sorry, I don't get you: if you need to pass four arguments then you have to pass all of them: I see no shortcut.

Kornfeld Eliyahu Peter 9-Jul-18 8:32am

class B
{
    public:
        B();
};

class B1 : public B
{
    public:
        B1() : B()
        {
            
        };
};

class C
{
    public:
        C();
};

class C1 : public C
{
    public:
        C1() : C()
        {
            
        };
};

class A
{
    public:
        A(B* b, C* c);
};


class A1 : public A
{
    public:
        A1(B* b, C* c, B1* b1, C1* c1) : A(b, c)
        {
            
        };
};

Hemal Shah 9-Jul-18 8:55am

HI KornfeldEliyahuPete,

Thanks for your reply.

Actually, I have implemented it in the same way as you implemented.

The problem comes now, whenever I call the constructor of A1, at that time I need to pass both B and B1 separately.
Before constructor call, I need to set fields in B and B1 separately (or copy), then I can use them in.

Kornfeld Eliyahu Peter 9-Jul-18 8:57am

I can't see any shortcut for that - you designed a setup where A1 has four parameters... You have to pass four parameters...

Hemal Shah 9-Jul-18 9:02am

Is there any alternative way, like use only B1 and C1 in A1's constructor, and construct A inside A1 constructor call. ?
In that case how to pass B and C ?

Kornfeld Eliyahu Peter 9-Jul-18 9:08am

It is possible, but may be a bad design (should A1 know how to create A?)...

Hemal Shah 9-Jul-18 9:22am

Yes A1 knows, it has to use B and C during A constructor call.
But IDK how to pass B and C inside A1, as I have just use B1 and C1 in A1's constructor argument.

Kornfeld Eliyahu Peter 9-Jul-18 9:28am

So?

class A1 : public A {
  public:
    A1(B1* b1, C1* c1) {
      // create b from b1 and c from c1
      // call base constructor
    }
};

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Jochen Arndt · Answer 1 · 2018-07-09T02:28:00

Solution 1

There is no need to pass copies. Just pass the pointers to the derived classes to the constructor of your base class A:

C++

class A1 : public A
{
public:
    A1(B1 *b1, C1 *c1) : A(b1, c1) {}
};

Posted 9-Jul-18 2:28am

Jochen Arndt

Comments

Kornfeld Eliyahu Peter 9-Jul-18 8:32am

It is true only if b and b1 are the same, but that not seems to be the case... Or at least not clearly the case...

Jochen Arndt 9-Jul-18 8:43am

It requires b1 to be a pointer to a class derived from B (and similar for c1 / C). That is what I have read out of the question:
"Base Classes are A, B, C and their respective Child classes are A1, B1, C1."

Kornfeld Eliyahu Peter · Answer 2 · 2018-07-09T02:48:00

Solution 2

Quote:
Before calling I have to prepare both b and b1 separately.
Is there any better way to implement it?

No.
As b and b1 are separate objects, you can not pass b to A in any other way...
(If b1 was only a cast of b, than it would be enough to pass b1)

Posted 9-Jul-18 2:48am

Kornfeld Eliyahu Peter