How to Call base Class Constructor

[Exceter]

hi
help me with the following plz, I have base class , it has two constructors, in derived class I want to call the base classes different constructors
for ex.,
class X {
public:
X();
X(int);
} ;
class Y : public X {
public:
Y();
f() {//call X()};
G() {//call X(int)};
};

how can I call in 1-function one constructor, and in second function second constructor of the base class?

tnx.

[kuphryn]

One solution is the :: operator.

X::X()

Kuphryn

[Kheun]

I would do it in the initialization list of the constructors.


class X
{
public:
X();
X(int);
} ;

class Y : public X
{
public:
Y():X() {};
Y(int i):X(i){};
};

[Paul McKenzie]

Originally posted by Exceter
class X {
public:
X();
X(int);
} ;
class Y : public X {
public:
Y();
f() {//call X()};
G() {//call X(int)};
};
There is a reason why those functions are called constructors. What you are asking is impossible. How can you call the constructor if the derived class has already been constructed? Constructors are only called when constructing objects.

If you want to call a function in class X, make it a regular (non-constructor) function and call it from your Y class.

class X {
public:
X() { DoXFunc(); }
X(int n) { DoX2Func(n); }

protected:
void DoXFunc() { }
void DoX2Func(int n) { }
};

class Y : public X {
public:
Y();
void f() { DoXFunc(); }
void G() { DoX2Func(1); }
};

And if from the Y constructor, you wanted to call a certain X constructor, you use something called a member-initialization list. But the bottom line is that you don't call constructors explictly, constructors are called automatically whenever you create an object.

Regards,

Paul McKenzie

[Paul McKenzie]

Originally posted by kuphryn
One solution is the :: operator.

X::X()

Kuphryn What compiler allows this? This is illegal syntax -- you can't call a constructor directly.

Regards,

Paul McKenzie