struct 做另一个struct的成员

最新推荐文章于 2022-12-21 10:14:56 发布

amaowolf

最新推荐文章于 2022-12-21 10:14:56 发布

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分类专栏： C_Linux 文章标签： struct timer date

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本文通过具体的C语言代码示例介绍了结构体之间的嵌套使用及结构体与指针的交互方式。演示了如何利用指针操作结构体成员，并展示了不同类型指针间的转换及其可能带来的风险。

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1. struct A 变量可以做另一个struct AB 的成员

2. struct A 的指针可以指向 struct AB 的变量

3. struct AB 的指针也可以指向 struct A的变量，but dangerous

4. 一切都在内存空间，只是指针指向而已。

/*
 * test.h
 *
 *  Created on: Sep 27, 2012
 *      Author: caoj7
 */

#ifndef TEST_H_
#define TEST_H_

struct date{
	int year;
	int month;
	int day;
};

typedef struct date date_t;

struct timer{
	date_t date_member;
	int hour;
	int minute;
	int second;
};

typedef struct timer timer_t;


#endif /* TEST_H_ */

/*
 * test.c
 *
 *  Created on: Sep 27, 2012
 *      Author: caoj7
 */
#include <stdio.h>
#include <stdlib.h>
#include "test.h"

date_t birth_date = {2012, 9, 26};

int main(void){

	timer_t birth_timer = {birth_date, 1,1,1};
	timer_t *birth_timer_ptr = &birth_timer;
	printf("birth_timer is: %d %d %d, %d:%d:%d\n",
			birth_timer_ptr->date_member.year,
			birth_timer_ptr->date_member.month,
			birth_timer_ptr->date_member.day,
			birth_timer_ptr->hour,
			birth_timer_ptr->minute,
			birth_timer_ptr->second
			);

	birth_timer_ptr->date_member.year =  2000;
	printf("not change value in orginal struct, birth_date.year = %d\n", birth_date.year);
	printf("birth_timer is: %d %d %d, %d:%d:%d\n",
				birth_timer_ptr->date_member.year,
				birth_timer_ptr->date_member.month,
				birth_timer_ptr->date_member.day,
				birth_timer_ptr->hour,
				birth_timer_ptr->minute,
				birth_timer_ptr->second
				);
	//let a member pointer point to a whole struct address
	date_t *date_ptr = (date_t *)birth_timer_ptr;
	printf("%d %d %d\n", date_ptr->year, date_ptr->month, date_ptr->day);

	//
	timer_t *test_timer_ptr = (timer_t *)date_ptr;
	printf("%d %d %d, %d:%d:%d\n",
			test_timer_ptr->date_member.year,
			test_timer_ptr->date_member.month,
			test_timer_ptr->date_member.day,
			test_timer_ptr->hour,
			test_timer_ptr->minute,
			test_timer_ptr->second);

	test_timer_ptr = (timer_t *)&birth_date;
	printf("%d %d %d, %d:%d:%d\n",
				test_timer_ptr->date_member.year,
				test_timer_ptr->date_member.month,
				test_timer_ptr->date_member.day,
				test_timer_ptr->hour,
				test_timer_ptr->minute,
				test_timer_ptr->second);

	return EXIT_SUCCESS;
}