VC ++ 6错误C2059：语法错误：'常量'

Question

Made this simple class with MSVC++ 6.0

class Strg
{
public:
    Strg(int max);
private:
    int _max;
};


Strg::Strg(int max)
{
  _max=max;
}

Sounds good if I use it in :

main()
{
  Strg mvar(10);
}

But Now If I use it in an another class :

class ok
{
public:
    Strg v(45);
};

I get message error : error C2059: syntax error : 'constant'

Could you tell me more please ?

Answer 1

Should be:

class ok
{
public:
    Strg v;
    ok() : v(45) {}
};

Non-static member variables that don't have default constructors (v in this case) should be initialized using initialization lists . In functions (like main) on the other hand you can use the regular constructor syntax.

Answer 2

What the compiler is complaining about is that you are trying to provide instruction on how ton instantiate the class member v inside your class definition, which is not allowed.

The place to instantiate v would be inside the contructor, or in the constructor's initializer list. For example:

Inside constructor:

class ok
{
public:
    Strg v;
    ok() {
        v = Strg(45);
    }
};

In initializer list:

class ok
{
public:
    Strg v;
    ok() : v(45) {}
};

The correct way to do it is the last one (otherwise, v would also require a default constructor and would be initialized twice).