C++内部结构--经典例子

最新推荐文章于 2025-12-09 11:28:31 发布

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#c++ #object #struct #class

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本文通过两个C语言示例展示了如何使用类型转换实现不同对象的行为变化。第一个示例使用了结构体，第二个示例则通过类的方式实现了类似的功能。通过宏定义进行类型转换，程序能够根据对象被视为不同类型来调用相应的方法。

例子1：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct object {
char name[16];
};

struct person {
char name[16];

void sleep() { printf("%s is person, he is sleeping/n", this->name); }
void study() { printf("%s is person, he is studying/n", this->name); }
};

struct dog {
char name[16];

void sleep() { printf("%s is dog, he is sleeping/n", this->name); }
void bark() { printf("%s is dog, he is barking/n", this->name); }
};

#define bless(object, type) ((type*) object)

int main()
{
struct object * o = (struct object *) malloc(sizeof(struct object));
strcpy(o->name, "tom");

       // 先把"tom"变为人
       bless(o, person)->sleep();
       bless(o, person)->study();

       // 再把"tom"变为狗
       bless(o, dog)->sleep();
       bless(o, dog)->bark();

       // 最后，再把"tom"变回人
       bless(o, person)->sleep();
       bless(o, person)->study();
       return 0;
}

// 程序运行时输出：
// tom is person, he is sleeping
// tom is person, he is studying
// tom is dog, he is sleeping
// tom is dog, he is barking
// tom is person, he is sleeping
// tom is person, he is studying

---------------------------------------------------------------------------------------------------------

例子2：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

class object {
public:
char ccc[20];
char bbb[20];
};

class person {
private:
char name[16];

public:
void sleep() { printf("%s is person, he is sleeping/n", this->name); }
void study() { printf("%s is person, he is studying/n", this->name); }
};

class dog {
private:
       char name[16];
public:
       void sleep() { printf("%s is dog, he is sleeping/n", this->name); }
       void bark() { printf("%s is dog, he is barking/n", this->name); }
};

#define bless(object, type) ((type*) object)

int main()
{
object * o = (object *)malloc(sizeof(object));
strcpy(o->ccc, "tom");

       // 先把"tom"变为人
       bless(o, person)->sleep();
       bless(o, person)->study();

       // 再把"tom"变为狗
       bless(o, dog)->sleep();
       bless(o, dog)->bark();

       // 最后，再把"tom"变回人
       bless(o, person)->sleep();
       bless(o, person)->study();
       return 0;
}