c++之结构体

一、结构体定义

结构体属于用户自定义的类型，允许用户存储不同的数据类型。

语法：struct 结构体名{结构体成员列表};

通过结构体创建变量有三种方式：

• struct 结构体名 变量名
• struct 结构体名 变量名={成员1值，成员2值...}
• 定义结构体时顺便创建变量

一般使用前两种，因为第三种在定义时创建的变量容易被人所忽略。

#include <iostream>
using namespace std;
struct Student {
    string name;
    int age;
    float score;
}s3;

int main() {    
    //创建的时候struct关键字可以省略
    struct Student s1;
    s1.name = "tom";
    s1.age = 12;
    s1.score = 99;
    cout << "name:" << s1.name << "age:" << s1.age << "score:" << s1.score << endl;
    struct Student s2 ={"jack", 15, 98};
    s3.name = "bob";
    s3.age = 19;
    s3.score = 97;
    system("pause");
    return 0;
}

二、结构体数组

作用：将自定义的结构体放入到数组中方便维护。

语法：struct 结构体名 数组名[元素个数] = {{},{},...{}}

#include <iostream>
using namespace std;
struct Student {
    string name;
    int age;
    float score;
};

int main() {    
    //结构体数组定义
    struct Student stuArr[3]
    {
        { "tom", 19, 99},
        { "jack",15, 98},
        { "bob", 22, 97 },
    };
    //可以修改值或者在这里进行赋值
    stuArr[2].name = "mike";
    //获取数组的长度
    int length = sizeof(stuArr) / sizeof(stuArr[0]);
    //遍历数组
    for (int i = 0; i < length; i++) {
        cout << stuArr[i].name << stuArr[i].age << stuArr[i].score << endl;
    }
    system("pause");
    return 0;
}

三、结构体指针

作用：通过指针来访问结构体中的成员

#include <iostream>
using namespace std;
struct Student {
    string name;
    int age;
    float score;
};

int main() {    
    struct Student s = { "tom",12,99 };
    Student* p = &s;
    //需要使用->来访问
    cout << p->name << p->age << p->score << endl;
    system("pause");
    return 0;
}

四、结构体嵌套结构体

#include <iostream>
using namespace std;

struct Student {
    string name;
    int age;
    float score;
};
struct Teacher {
    int id;
    string name;
    int age;
    Student stu;
};


int main() {
    struct Teacher t;
    t.id = 1;
    t.name = "joke";
    t.age = 45;
    struct Student stu = { "tom",12,99 };
    t.stu = stu;
    cout << t.id << t.name << t.age << t.stu.name << t.stu.age << t.stu.score << endl;
    system("pause");
    return 0;
}

五。结构体做函数参数

作用：将结构体作为参数向函数传递。

传递方式有两种：值传递、引用传递。

值传递：

#include <iostream>
using namespace std;

struct Student {
    string name;
    int age;
    float score;
};

//值传递
void printStudent(Student stu) {
    stu.name = "jack";
    stu.age = 22;
    stu.score = 90;
    cout << "结构体中的stu信息：" << endl;
    cout << stu.name << "," << stu.age << "," << stu.score << endl;
}


int main() {
    struct Student stu = { "tom",12,99 };
    cout << "未传入函数之前的结构体值：" << endl;
    cout << stu.name << "," << stu.age << "," << stu.score << endl;
    printStudent(stu);
    cout << "传入函数之后的结构体值：" << endl;
    cout << stu.name << "," << stu.age << "," << stu.score<< endl;
    system("pause");
    return 0;
}

输出：

引用传递：

#include <iostream>
using namespace std;

struct Student {
    string name;
    int age;
    float score;
};

//值传递
void printStudent(Student* stu) {
    stu->name = "jack";
    stu->age = 22;
    stu->score = 90;
    cout << "结构体中的stu信息：" << endl;
    cout << stu->name << "," << stu->age << "," << stu->score << endl;
}


int main() {
    struct Student stu = { "tom",12,99 };
    struct Student* p = &stu;
    cout << "未传入函数之前的结构体值：" << endl;
    cout << stu.name << "," << stu.age << "," << stu.score << endl;
    printStudent(p);
    cout << "传入函数之后的结构体值：" << endl;
    cout << stu.name << "," << stu.age << "," << stu.score << endl;
    system("pause");
    return 0;
}

输出：

六、结构体中const的使用场景

作用：用const防止误操作 

#include <iostream>
using namespace std;

struct Student {
    string name;
    int age;
    float score;
};

//值传递
void printStudent(const Student* stu) {
    /*这里就不能进行修改了
    stu->name = "jack";
    stu->age = 22;
    stu->score = 90;
    */
    cout << "结构体中的stu信息：" << endl;
    cout << stu->name << "," << stu->age << "," << stu->score << endl;
}


int main() {
    struct Student stu = { "tom",12,99 };
    struct Student* p = &stu;
    cout << "未传入函数之前的结构体值：" << endl;
    cout << stu.name << "," << stu.age << "," << stu.score << endl;
    printStudent(p);
    cout << "传入函数之后的结构体值：" << endl;
    cout << stu.name << "," << stu.age << "," << stu.score << endl;
    system("pause");
    return 0;
}

输出：

只需要记住，用const修饰的数据类型就不能再进行更改。