Question

I’m just starting my own Windows API wrapper and I’ve run into an unfamiliar topic while rewriting a structure to include C++ features.

I’m turning this:

typedef struct _RECT {
    LONG left;
    LONG top;
    LONG right;
    LONG bottom;
} RECT, *PRECT;

into

#define RECT_POS 1
#define RECT_SIZE 2

typedef struct WrapperRect // RECT
{
    WrapperRect(); // all 0
    WrapperRect (const double, const double, const double, const double, bool = RECT_POS); // initalize with tl pos and either br pos or size

    bool set (const double, const double, const double, const double, bool = RECT_POS); // set tl pos and either br pos or size
    bool pos (const double, const double); // set tl pos
    bool size (const double, const double); // set size

    WrapperRect & operator= (const WrapperRect &); // assign another rect
    bool operator== (const WrapperRect &); // check for equality (pos+size)
    bool operator!= (const WrapperRect &); // check for inequality (pos+size)
    bool operator> (const WrapperRect &); // check for tl pos greater
    bool operator< (const WrapperRect &); // check for tl pos less
    bool operator>= (const WrapperRect &); // check for tl pos greater equal
    bool operator<= (const WrapperRect &); // check for tl pos less equal
    WrapperRect & operator+ (const POINT &); // move down/right
    WrapperRect & operator- (const POINT &); // move up/left
    WrapperRect & operator+= (const POINT &); // move down/right
    WrapperRect & operator-= (const POINT &); // move up/left

    double l, left, x; // left
    double r, right; // right
    double t, top, y; // top
    double b, bottom; // bottom

    double w, width; // width
    double h, height; // height
} Rect, rect; // allow more convenient names

My only problem is that if the user were to say

Rect myRect;  
myRect.right = 50;

it will set the right side, but won’t be able to change the aliases for the right side, or the width.

I don’t want the members to be private either because I want the

cout << myRect.x;

syntax rather than the annoying

cout << myRect.getX();

syntax.
Is there any way to achieve this, or must I use get functions?

edit:
I really wasn’t thinking when I wrote this, I’ve added some return values (>.>) and changed the double in operator+ etc to a point. I’m starting to try the possibilities before I accept one.

Answer 1

It is quite bad practice to expose your data members. It is also really bad practice to have multiple copies of the exact same information inside your classes. It is both inefficient and bug-prone.

You definitely need to use accessor functions.

That being said, you don’t need to have getX(); – just x() would be fine.

If you’re really set on avoiding function syntax, something like this would be ok I guess:

struct Rect
{
private:
    double l, r, t, b;

public:
    const double &x, &y;

    Rect() : x(r), y(t) {}

    ...etc.
};

Then you could use r.x in a safe fashion though you are still somewhat exposing your implementation.