static members

[Ceset]

hi everyone

in .h

class chickens
{
private:
    static Window * mWin;
    static Renderer * mRen;
public:
    ....
    ....
    Window * GetWindow();
    Renderer * GetRenderer();
};

and called it in .cpp

Window * chickens::GetWindow()
{
    return Window * chickens::mWin;
}

Renderer * chickens::GetRenderer()
{
    return Renderer * chickens::mRen;
}

and the compiler gives this error

C:\Users\Ceset\Projects\Chickens\Classes\chickens.cpp:31: error: expected primary-expression before '*' token
     return Window * chickens::mWin;
                   ^

C:\Users\Ceset\Projects\Chickens\Classes\chickens.cpp:36: error: expected primary-expression before '*' token
     return Renderer * chickens::mRen;
                     ^

sorry i didnot get exactly static members in classes even though i read many times and google research also could not help. Can you tell me why it gives this error and how should i use statics in a class

[Disch]

Window * chickens::GetWindow()
{
//  return Window * chickens::mWin;  <- no
    return mWin;  // <- yes
}

You only put the type before the variable when you are declaring/defining the variable.

You also don't need the chickens:: scope resolution here because you're already in the chickens class. (though adding it doesn't hurt, I suppose).

[Ceset]

i did it this way

Window * chickens::GetWindow()
{
    return mWin;
}

Renderer * chickens::GetRenderer()
{
    return mRen;
}

and it gives this error now

C:\Users\Ceset\Projects\Chickens\Classes\chickens.cpp:11: error: undefined reference to `chickens::mWin'
.....
.....

EDIT: i know what i did was nonsense. but in google people says i need to redefine(or such i couldnt get much) the variable to make linker happy(???).

[Disch]

Declaration of static member vars isn't enough, you also need to "define" them so the linker knows where to put them.

In your cpp file, add these:

Window * chickens::mWin;
Renderer * chickens::mRen;

[Ceset]

thx that solved th problem

[gpoat]

// Add these lines and it should compile.

Window * chickens::mWin = nullptr; // or whatenever initial address you want.
Renderer * chickens::mRen = nullptr; // idem


//It would be better to scope it with the class name

Window * chickens::GetWindow()
{
    return chickens::mWin;
}

Renderer * chickens::GetRenderer()
{
    return chickens::mRen;
}