Object-Oriented Programming with C language (2)

The previous set provides an intuitive introduction to oosm macro packages and Their Applications. Let's take a look at the specific descriptions of CCIRC, crect, csqua, and other objects.

An interface abstracts behaviors and can be used to implement class polymorphism. IMEAS. h defines an interface for measuring the circumference and area:

#ifndef __IMEAS_H__#define __IMEAS_H__#include "oosm.h"/* Measuring Interface, for measuring the perimeter and area of objects */interface(imeas){    double (*peri)(void* this); /* for measuring the perimeter of objects */    double (*area)(void* this); /* for measuring the area of objects */};#endif/*__IMEAS_H__*/

Because the interface is abstract, pay special attention to declaring this pointer as the void * type, which makes it easier to convert the pointer.
Classes have attributes and methods, and polymorphism methods use interfaces to achieve their goals. crect. h/crect. c defines and implements a rectangular class:

#ifndef __CRECT_H__#define __CRECT_H__#include "imeas.h"/* Rectangle Class, for describing rectangle objects */class(crect){    implements(imeas);  /* Implements imeas interface */    double width;    double height;};#endif/*__CRECT_H__*/

#include "crect.h"static double peri(void* this){    return 2 * (((crect*)this)->width + ((crect*)this)->height);}static double area(void* this){    return ((crect*)this)->width * ((crect*)this)->height;}constructor(crect){    mapping(imeas.peri, peri);    mapping(imeas.area, area);}destructor(crect){    return 1;   /* Returns 1 for freeing the memory */}

The constructor is mainly used for method ing. Here we implement the methods in the IMEAS interface, so pay special attention to writing the ing as IMEAS. peri/IMEAS. area, the crect_new macro function is automatically generated after the construction. In destructor, you can release the internal space and then return 1 to delete itself. After the analysis, the crect_delete macro function is automatically generated.

Similarly, CCIR. h/CCIR. c defines circular classes:

#ifndef __CCIRC_H__#define __CCIRC_H__#include "imeas.h"/* Circle Class, for describing circular objects */class(ccirc){    implements(imeas);  /* Implements imeas interface */    double radius;    double (*diam)(ccirc* this);    /* for measuring the diameter of the circular objects */};#endif/*__CCIRC_H__*/

#include "ccirc.h"#define PI  (3.1415926)static double peri(void* this){    return 2 * PI * ((ccirc*)this)->radius;}static double area(void* this){    return PI * ((ccirc*)this)->radius * ((ccirc*)this)->radius;}static double diam(ccirc* this){    return 2 * this->radius;}constructor(ccirc){    mapping(imeas.peri, peri);    mapping(imeas.area, area);    mapping(diam, diam);}destructor(ccirc){    return 1;   /* Returns 1 for freeing the memory */}

On the basis of implementing the IMEAS interface, the circular class also has its own diam method. Pay attention to the direct ing of its own method.