Javer 学 c++(九)：结构体篇

总览

定义和使用

通过结构体创建变量的方式有三种，见下代码：

#include <iostream>
using namespace std;

struct Student {
    string name;
    int age;
    int score;
}s3;

int main() {

    // 创建方式一：创建空的然后赋值
    struct Student s1;
    s1.name = "John";
    s1.age = 18;
    s1.score = 10;
    cout << s1.name << " " << s1.age << " " << s1.score << endl;
    // 创建方式二
    struct  Student s2 = {"River", 18, 100 };
    // 创建方式三:定义结构体的时候顺手的事
    s3.name = "Jewel";
    s3.age = 18;
    s3.score = 10;

}

结构体指针

通过指针->来访问结构体的成员

#include <iostream>
using namespace std;

struct Student {
    string name;
    int age;
    int score;
}s3;

int main() {

    Student s = {"River", 20, 100};
    Student * p = &s;
    // 使用 -> 箭头来访问
    cout << p->name << " " << p->age << " " << p->score << endl;

}

结构体嵌套结构体

结构体的成员可以是另一个结构体

#include <iostream>
using namespace std;

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

struct Teacher {
    int id;
    string name;
    int age;
    Student student;
};

int main() {

    Teacher t;
    t.id = 2;
    t.name = "John";
    t.age = 10;

    t.student = {"River", 10, 20};

    return 0;
}

结构体做函数参数

将结构体作为参数向函数中传递： 值传递 or 引用传递

#include <iostream>
using namespace std;

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

// 值传递
void printStudent1(Student student) {
    student.age = 10; // 值传递：原来的对象值不变
    cout << student.name << student.age << student.score << endl;
}

// 地址传递
void printStudent2(Student * p) {
    p->age = 10; // 地址传递：原来的对象值会变
    cout << p->name << p->age << p->score << endl;
}

int main() {

    Student student = {"River", 10, 20};

    printStudent1(student);

    Student * p = &student;
    printStudent2(p);

    return 0;
}

结构体中 const 的使用

作用：用 const 来防止误操作

#include <iostream>
using namespace std;

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

// 地址传递
void printStudent2(const Student * p) {
    p->age = 10; // 报错，因为是 const，解决了引用误操作的问题
    cout << p->name << p->age << p->score << endl;
}

int main() {

    Student student = {"River", 10, 20};

    Student * p = &student;
    printStudent2(p);

    return 0;
}