C语言结构体学习系列之（二）

1，结构体做函数参数，应该注意的是，再被调用函数中改变结构体的值与普通变量的方法一样，不能直接定义两个普通形参接收，然后修改形参，这只是修改了形参的值，正确的方法是定义一个指针，然后把结构体地址传给指针，然后用指针进行修改。例：

void copyTeacher(T to, T from)
{
to = from;
}

void copyTeacher2(T *to, T *from)
{
//(*to) = (*from);
*to = *from;
}
void main12()
{
T tone = { "aaaa", 32, 02 };
T ttwo;
//copyTeacher(ttwo, tone);
//printf("copyTeacher()after \n");
//printf("ttwo.name = %s\n", ttwo.name);
//printf("ttwo.age = %d", ttwo.age);

copyTeacher2(&ttwo, &tone);
printf("copyTeacher()after \n");
printf("ttwo.name = %s\n", ttwo.name);
printf("ttwo.age = %d", ttwo.age);
system("pause");

}

我们可以看到，调用copyTeacher（）函数最后打印的是一堆乱码，

而调用copyTeacher2（）函数打印的是正确的。

2，结构体做函数参数的例程：

#define  _CRT_SECURE_NO_WARNINGS
#include <stdlib.h>
#include <stdio.h>

typedef struct Teacher
{
char name[64];
int age;
int id;

}Teacher;

void printTeacher(Teacher *Array, int num)
{
int i = 0;
for (i = 0; i < num; i++)
{
printf("age:%d\n", Array[i].age);
}
}

void sortTeacher(Teacher *Array, int num)
{
int i, j;
Teacher tmp;
for (i = 0; i < num; i++)
{
for (j = i + 1; j < num; j++)
{
if (Array[i].age>Array[j].age)
{
tmp = Array[i];
Array[i] = Array[j];
Array[j] = tmp;
}
}
}
}

Teacher * createTeacher(int num)
{
Teacher *tmp = NULL;
tmp = (Teacher *)malloc(sizeof(Teacher)*num);
if (tmp == NULL)
{
return NULL;
}
}
int createTeacher2(Teacher **p, int num)
{
Teacher *tmp = NULL;
tmp = (Teacher *)malloc(sizeof(Teacher)*num);
if (tmp == NULL)
{
return -1;
}
*p = tmp;   //二级指针形参去间接修改 实参的值
return 0;
}

void FreeTeacher(Teacher *p)
{
if (p != NULL)
{
free(p);
}
}
void main()
{
int i = 0;
//Teacher Array[3];
int num = 3;
Teacher *pArray = NULL;
createTeacher2(&pArray,num);
if (pArray == NULL)
{
return;
}
for (i = 0; i < num; i++)
{
printf("\nplease enter age:");
scanf("%d", &(pArray[i].age));
}

printTeacher(pArray, num);

sortTeacher(pArray, num);

printf("排序之后：\n");
printTeacher(pArray, num);
free(pArray);
pArray = NULL;
system("pause");
}