Doing something when a variable is changed

I have a CGButton class again and then I have four variables (left, top, width, height). When the user changes any of these variables, I want to move the button using API. Is it even possible or will I have to use a function like "Move", "Resize", or something else?

You can do it with MoveWindow I guess, look it up at MSDN...

Make sure you use Properties rather than just a public variable...
than you should be fine...
you know how to call MoveWindow right, so make a property like this:

PHP Code:

---

property void set_Left (int value){
//MoveWindow with the new value of Left
} 


---

The keyword "property" doesn't exist.:confused:

__declspec(property) comes into it somewhere.

You should make a class with get_variable(value) and set_variable(value).

The problem with __declspec(property) is that it is MSVC specific, and thus not portable.

You can use this macro, to make the code portable (and make it look a little more ugly):

Code:

---

#include <iostream>

// The PPLG macro allows you to
//  make public memember variables
//  with custom get/let functions
#define PPLG(TYPE, VARNAME) \
private: \
    class VARNAME{ \
        public: \
        inline TYPE operator = (TYPE param) {return let(param);} \
                inline operator TYPE () {return get();}; \
        private: \
            TYPE val; \
                TYPE let (TYPE param); \
                TYPE get (); \
        }; \
public: \
        VARNAME VARNAME;


// A test class
class a{
public:
        PPLG(int,b); //We have a member 'b', of type int
};


// The get & let functions
int a::b::get(){
        return val;
}
int a::b::let(int param){
        std::cout << "Variable set to " << param << std::endl;
        return val=param;
}

// A sample main function
int main(){
        a test_a;
        test_a.b = 10;
        test_a.b = test_a.b + 1;
        return 0;
}

---

I always found my preferred method (non-declspec) to be:

Code:

---

class test {
public:
    inline test() : m_propname(0) { }

    inline int propname() const { return m_propname; }
    void propname(int pn) { m_propname = pn; }

private:
    int m_propname;
}

---

:)

parksie: Something like that is probably better. My macro-using solution was only to show that it's posible to do it. It will make the program harder to understand, since it uses sub-classes hidden away in macros.

Anything is possible ;) Whether you should do it is another matter :D

I think macros are "discouraged" in C++ for the reasons you gave.

Ok thanks. I guess I'll the use the method of set_property or get_property because it's pretty straight forward.

hmm I suggest Parksie's way to do it... that looks almost like a property...
the thing I suggested was for Managed C++ (.NET), I didn't realize it was the Managed version... don't use it ;)