How do I use structs in C to emulate classes?

Follow below example program: typedef struct object object, *setCoordinates; struct object { float x, y; void (*setCoordinates)(object *self, float x, float y); void (*getYCoordinate)(object *self); void (*getXCoordinate)(object *self); }; void object_setCoordinates(object *self, float x, float y){ self->x = x; self->y = y; } float object_getXCoordinate(object *self){ return self->x; } float object_getYCoordinate(object *self){ return self->y; } object point; point.setCoordinates = object_setCoordinates; point.getYCoordinate = object_getYCoordinate; point.getXCoordinate = object_getXCoordinate; point.setCoordinates(&point, 1, 2); printf("Coordinates: X Coordinate: %f, Y Coordinate: %f", point.getXCoordinate, point.getYCoordinate); read less

Classes are structures with a hidden pointer to a table of function pointers called VTable. The Vtable itself is static. When types point to Vtables with the same structure but where pointers point to other implementation, you get polymorphism. It is recommended to encapsulate the calls logic in function that take the struct as parameter to avoid code clutter. You should also encapsulate structures instantiation and initialization in functions (this is equivalent to a C++ constructor) and deletion (destructor in C++). These are good practice anyway. typedef struct { int (*SomeFunction)(TheClass* this, int i); void (*OtherFunction)(TheClass* this, char* c); } VTable; typedef struct { VTable* pVTable; int member; } TheClass; To call the function int CallSomeFunction(TheClass* this, int i) { (this->pVTable->SomeFunction)(this, i); } read less