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mohandes_philip

Using Function Pointers in class declaration

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Hi I recently write a class that manage DirectX surfaces. In my class i must choose a proper function upon on a color mode. For example if display color-mode was 16-Bit the class must choose putPixel16() member function and if display color-mode was 24-Bit choose putPixel24() member function. The class might be : class CSurface { private: void putPixel16(int x, int y, int clr); void putPixel24(int x, int y, int clr); public: void (*putPixel)(int x, int y, int clr); }; For this i decide to use "Function Pointer" but i dont really know how use it and if it's true...? If i can use "Function Pointer" i must assign putpixel public member function to one of 2 private member function putPixel16() and putPixel24(). Then if you want to plot a pixel on surface you can use public member putPixel that basically is a "Function Pointer". Is my style true for this reason...? If you have some idea please send to topic. Thank you.

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It looks like you have the right idea, more or less. You would assign a value to the function pointer like this:
putPixel = &CSurface::putPixel16;
And invoke the function like this:
this->*putPixel(...);
I don't work with this syntax much these days, so the above may or may not be exactly correct (just Google 'C++ member function pointers' and I'm sure you'll find some other code examples to refer to).

Now, calling a function through a pointer on a per-pixel basis sounds a bit iffy to me, but then again I don't know what you're doing exactly. Just be aware that there are probably other ways you could approach the problem (e.g. templates).

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