asked on

constructor inside a constructor

Can I create a constructor inside an other constructor, by passing the parameters of the first constructor to the second constructor

Sample code:

Reservation::Reservation(Trucks* tptr, Customer* cptr)
{
      cout<<"\nEnter Reservation date";
      cin>>Res_Date;//overloading required
      cout<<"\nEnter Pick Date";
      cin>>Pick_Date;
      cout<<"\nEnter Reservation id";
      cin>>Res_Id;
      cout<<"\nEnter the contract time period";
      cin>>Contract;
      cout<<"\nEnter VIN number";
      cin>> (tptr->VIN);
      cout<<"\nEnter License number";
      cin>>(cptr->Licence_No);
//////////now passing these values to create a onject
Reservation R=new Reservation(Res_Date,Pick_Date, Res_Id,Contract,tptr->VIN,cptr->Licence_No);
}

rstaveley

Yes, it works. You'll need to meake sure that the ctor(s) that don't create a new R initialise it as NULL to make the dtor work.

Illustration:
--------8<--------
#include <iostream>
using std::cout;

class foo {
      foo *p;
public:      foo() : p(0) {
            std::cout << "ctor()\n";
      }
      foo(int) : p(new foo) {
            std::cout << "ctor(int)\n";
      }
      ~foo() {
            std::cout << "dtor (p=" << static_cast<void*>(p) << ")\n";
            delete p; // Deleting a NULL pointer is OK per the standard
      }
};

int main()
{
      foo p(1);
}
--------8<--------

bkfirebird

The parameters of the second constructor seem to be different from the first one ...... in that case it should not be a problem

rstaveley

BTW... Be careful about copy ctors and the assignment operator. Probably you ought to make them private to avoid having to think about them.

itsmeandnobodyelse

>> Can I create a constructor inside an other constructor
>> Yes, it works.

I got the impression that question and answers talk of two different things:

If you want to implement one constructor by calling a second constructor like that:

class A
{
int m_i;
public:
A(bool b) { m_i = b? 1 : 0; }
A(int i) : A(false) {}
};

you'll get an error 'illegal member initialization: 'A' is not a base or member'.

So, you could only use another constructor to construct the 'this' object by using a baseclass constructor.

Regards, Alex

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sonstkeiner

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sonstkeiner

Oops, forgot to state input's return type, but you probably noticed that (Reservation *, of course).
Thanks fo accepting the answer anyway (;-).