【C】Re09 结构体

一、结构体 Struct

创建和基本使用

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

// 自定义数据类型 : 结构体
struct Person {
    int age;
    char id[18];
    char name[20];
    int gender;
};

// 创建结构体数据类型
void createStructType ( ) {
    struct Person man = {
            23,
            "363301199804023324",
            "tom",
            1
    };

    // 访问结构体数据通过点
    printf("man age -> %d\n", man.age);
    printf("man id -> %s\n", man.id);
    printf("man name -> %s\n", man.name);
    printf("man gender -> %d\n", man.gender);
}

// 方式二 声明结构体之后附加变量名称
struct Ac {
    int property1;
    char property2[18];
    char property3[20];
    int property4;
} sss; // 再后面声明变量名称

void createStructType2() {
    sss.property1 = 12;
    // 不可以直接赋值  sss.property2 = "sdas";
    strcpy(sss.property2, "sss");
}


int main() {
    createStructType();

    return 0;
}

属性值的交换：

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

struct Struct {
    int property1;
    char property2[10];
    double property3;
};
// 赋值操作
void structAssignment() {
    struct Struct s1;
    struct Struct s2 = {
            22,
            "张三",
            22.55
    };

    // 赋值方式1 为s1 逐个赋值操作
    s1.property1 = s2.property1;
    strcpy(s1.property2, s2.property2);
    s1.property3 = s2.property3;

    // 赋值方式2 允许操作整体赋值的方式
    s1 = s2;

    // 赋值方式3 使用memcpy函数
    memcpy(&s1, &s2, sizeof(struct Struct));
}
// 属性值交换操作
void structPropertyChange() {
    struct Struct s1 = {
            10,
            "李四",
            100.23
    };
    struct Struct s2 = {
            22,
            "张三",
            22.55
    };

    int property1Temp = s1.property1;
    s1.property1 = s2.property1;
    s2.property1 = property1Temp;

    // char property2Temp[10] = s1.property2;
    char property2Temp[10];
    strcpy(property2Temp, s1.property2);
    strcpy(s1.property2, s2.property2);
    strcpy(s2.property2, property2Temp);

    double property3Temp = s1.property3;
    s1.property3 = s2.property3;
    s2.property3 = property3Temp;

    // 结构体允许整体作为一个TEMP进行交换操作
    struct Struct tempStruct;
    tempStruct = s1;
    s1 = s2;
    s2 = tempStruct;
}

int main() {
    structPropertyChange();
    return 0;
}

结构体数组：

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

struct Struct {
    int property1;
    char property2[10];
    double property3;
};

void structArray() {
    struct Struct structs[5] =  {
            {1,"张三1", 23.23},
            {2,"张三2", 23.23},
            {3,"张三3", 23.23},
            {4,"张三4", 23.23},
            {5,"张三5", 23.23},
    };

    int size = sizeof(structs) / sizeof(struct Struct);

    for (int i = 0; i < size; ++i) {
        printf(
                "element%d p1 : %d p2 : %s, p3 : %.2f\n",
                i,
                structs[i].property1,
                structs[i].property2,
                structs[i].property3
                );
    }
}

int main() {
    structArray();
    return 0;
}

嵌套的结构体：

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

// 结构体嵌套
struct Student {
    char stuID[10];
    char name[4];
};
struct Teacher {
    char teachID[5];
    char name[4];
    struct Student student;
};


void structNesting() {
    // 嵌套结构体创建方式
    struct Teacher li = {
            "133001",
            "李四",
            { "122001", "小明"}
    };
    // 允许修饰括号进行赋值
    struct Teacher jie = {
            "133002",
            "杰哥",
            "122001",
            "小明"
    };
    
    // 调用
    printf(
            "nestingStructs -> teacherID : %s, name : %s, stuID : %s, stuName : %s\n",
            li.teachID,
            li.name,
            li.student.stuID,
            li.student.name
            );
}

int main() {
    structNesting();
    return 0;
}

二、结构体和指针

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

// 结构体与指针
struct Student {
    int id;
    char name[4];
    double score;
};

void structWithPointer () {
    struct Student student = { 1, "Tom", 98.5 };
    struct Student * studentPointer = &student; // 结构体指针

    // 使用指针调用结构体属性的方式
    printf(
            "use studentPointer to get properties :\n id : %d, name : %s, score : %.2f\n",
            studentPointer -> id,
            studentPointer -> name,
            studentPointer -> score
            );
    // 使用结构体属性的方式调用：
    printf(
            "use structVariable to get properties :\n id : %d, name : %s, score : %.2f\n",
            student.id,
            student.name,
            student.score
    );

    // 使用解引用 == 结构体变量
    printf(
            "use *studentPointer to get properties :\n id : %d, name : %s, score : %.2f\n",
            (*studentPointer).id,
            (*studentPointer).name,
            (*studentPointer).score
    );

    // 使用解地址 == 结构体指针
    printf(
            "use &student to get properties :\n id : %d, name : %s, score : %.2f\n",
            (&student) -> id,
            (&student) -> name,
            (&student) -> score
    );
}

int main() {
    structWithPointer ();
    return 0;
}

 三、结构体与堆区

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct Student {
    int id;
    char * name;
    int age;
};

void test() {
    struct Student student = {
            12003,
            "aaa",
            23
    };

    printf("name -> %s\n", student.name);

//    student.name[0] = 'A'; 不允许这样操作，aaa是字符串常量，无法被修改

    printf("name -> %s\n", student.name);
}
void test2() {
    struct Student student = {
            12003,
            NULL,
            23
    };

    student.name = malloc(sizeof(char) * 64); // 结构体属性值创建在malloc堆区中
    strcpy(student.name, "Jerry");
    printf("name -> %s\n", student.name);

    strcpy(student.name, "Tom");
    printf("name -> %s\n", student.name);
}

void customFree(void * pointer) {
    if (pointer != NULL) {
        free(pointer);
        pointer = NULL;
    }
}

void test3() {
    // 结构体本身和属性成员都在堆区中创建
    struct Student * studentPointer = NULL;
    studentPointer = malloc(sizeof(struct Student));

    studentPointer -> id = 1002001;
    studentPointer -> name = "Ach";
    studentPointer -> age = 22;
    printf("id - %d, name - %s, age - %d\n", studentPointer->id, studentPointer->name, studentPointer->age);

    customFree(&studentPointer->id);
    customFree(studentPointer->name);
    customFree(&studentPointer->age);

    printf("id - %d, name - %s, age - %d\n", studentPointer->id, studentPointer->name, studentPointer->age);

}

int main() {
    test3();
    return 0;
}

四、Const与结构体：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct Student {
    int id;
    char * name;
    int age;
};

void sss() {
    struct Student s1 = {
            100,
            "Tom",
            18
    };

    struct Student const * p1 = &s1; // 常量指针，指针指向的内存空间不可以改变存储值，但是改变指向
    struct Student * const p2 = &s1; // 指针常量，指向不可以改变，但是可以改变指向的内存空间存储值
    struct Student const * const p3 = &s1; // 常量锁定，不可以操作任何的写入了
}

int main() {
    sss();
    return 0;
}