Constructor in C++

[Allerdyce.John]

Hi,

I have 2 classes:

class A {
public:
A();
A(int i);
};

class B: public A {
pubilc:
B(int i);
};

If I don't have constructor B(), does it call A() automatically?

Can I do this:
B b; // B does not have default constructor but A has.

 

[Alf P. Steinbach]

* (e-mail address removed):

Hi,

I have 2 classes:

class A {
public:
A();
A(int i);
};

class B: public A {
pubilc:

B(int i);
};

If I don't have constructor B(), does it call A() automatically?

If you don't have a constructor B() it doesn't exist; C++ only generates
one for you if you don't declare any constructors at all.

Can I do this:
B b; // B does not have default constructor but A has.

Nope.

 

[Allerdyce.John]

If I have
class A {
public
A(int i);
}

public B{
public:
virtual void abstractFunciton = 0;
}

public C{
public:
C(int i);
};

how can I call A' constructor A(int i) from C(int i).

I try
C::C(int i): A(i) {
}
it does not compile.

 

[Alf P. Steinbach]

* (e-mail address removed):

If I have
class A {
public
A(int i);
}

public B{
public:
virtual void abstractFunciton = 0;
}

public C{
public:
C(int i);
};

how can I call A' constructor A(int i) from C(int i).

I try
C::C(int i): A(i) {
}
it does not compile.

C does not derive from A.

 

[Victor Bazarov]

If I have
class A {
public
A(int i);
} ;

public B{
public:
virtual void abstractFunciton = 0;

virtual void pureFunction() = 0;

} ;

public C{
public:
C(int i);
};

how can I call A' constructor A(int i) from C(int i).

I try
C::C(int i): A(i) {
}
it does not compile.

You need to derive 'C' from 'A' first to do that.

V