C语言学习014:结构化数据类型

struct的基本使用

 #include <stdio.h>

 //定义数据结构
 struct fish{
     const char *name;
     const char *species;
     int teeth;
     int age;
 };

 void catalog(struct fish f){
     printf("%s is a %s with %i teeth. He is %i\n",f.name,f.species,f.teeth,f.age);//访问结构的字段
 }

 int main(){
     //声明结构变量
     struct fish snappy={"Snappy","Piranha",,};
     catalog(snappy);
     return ;
 }

　　将结构变量赋值给另一个结构变量时，计算机会创建一个全新的结构副本，然后将每个字段都复制过去；如果结构中有指针，那么复制的仅仅是指针的值

    struct fish snappy={"Snappy","Piranha",,};
    struct fish gnasher=snappy;

　　结构还可以嵌套使用

 #include <stdio.h>

 struct preferences{
     const char *food;
     float exercise_hours;
 };

 struct fish{
     const char *name;
     const char *species;
     int teeth;
     int age;
     struct preferences care;//嵌套在fish中的结构体preferences
 };

 void catalog(struct fish f){
     printf("%s is a %s with %i teeth. He is %i\n",f.name,f.species,f.teeth,f.age);//访问结构的字段
     //访问结构体中的结构体
     printf("%s like to eat %s\n",f.name,f.care.food);
     printf("%s like to exercise %f hours\n",f.name,f.care.exercise_hours);
 }

 int main(){
     struct fish snappy={"Snappy","Piranha",,,{"Meat",7.5}};
     catalog(snappy);
     return ;
 }

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更简单的创建结构变量

　　通过使用typedef为结构命名，这样在创建结构变量的时候可以省去struct关键字

#include <stdio.h>

typedef struct cell_phone{
    int cell_no;
    const char *wallpapaer;
} phone;//phone为类型名（cell_phone的别名）

int main(){
     phone p={,"sinatra.png"};
     printf("number %i\n",p.cell_no);
    return ;
}

　　我们还可以直接省去结构的名字定义结构，这也就是所谓的匿名结构

 typedef struct {
     int cell_no;
     const char *wallpapaer;
 } phone;

传递结构指针

　　当将一个结构赋值给另一个结构，我们知道是创建一个新的副本；如果我们希望通过被赋值的结构更新原来的结构，就需要用到结构指针

 #include <stdio.h>

 typedef struct {
     int cell_no;
     const char *wallpapaer;
 } phone;

 int main(){
      phone p={,"sinatra.png"};
      phone p2=p;
      p2.cell_no=;
      printf("p.cell_no:%i p2.cell_no:%i\n",p.cell_no,p2.cell_no);
      phone* p3=&p;//将结构p的地址赋值给*p3
      (*p3).cell_no=;
      printf("p.cell_no:%i p2.cell_no:%i p3.cell_no:%i\n",p.cell_no,p2.cell_no,(*p3).cell_no);
     return ;
 }

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　　因为我们常常会把(*p2).wallpapaer错误的写成*p2.wallpapaer，它们并不等价，所以C语言开发者设计了更简单的表示结构指针的方法

 int main(){
      phone p={,"sinatra.png"};
      phone* p2=&p;
      printf("p2->wallpapaer:%s = (*p2).wallpapaer:%s\n",p2->wallpapaer,(*p2).wallpapaer);//
     return ;
 }

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