【C++】結構體/結構體數組/結構體指針/結構體嵌套/函數參數/const

一、結構體聲明

struct Student
{
      //成員列表
      string name;
      int age;
      int score;
}; //s3;定義時直接聲明

int main()
{
      struct Student s1;
//法一、直接賦值
      s1.name = "Apple";
      s1.age = 10;
//法二、直接聲明
      struct Student s2 = {"Banana", 19, 80}; //不可跳着聲明
}

二、結構體數組
//創建結構體數組

int main()
{
      struct Student stuArray[3] = 
      {
            {"Apple", 19, 80},
            {"Banana", 18, 99},
            {"Cat", 17, 70}
      }; //注意逗號，分號的位置
}

//給結構數組中賦值

int main()
{
    struct Student stuArray[3] = 
    {
        {"Apple", 19, 80},
        {"Banana", 18, 99},
        {"Cat", 17, 70}
    };
    
    stuArray[0].name = "Dog";

    cout << stuArray[0].name << stuArray[0].score <<endl;
    system("pause");
}

//遍歷結構體數組：for循環

三、結構體指針

int main()
{
    struct Student stuArray[3] = 
    {
        {"Apple", 19, 80},
        {"Banana", 18, 99},
        {"Cat", 17, 70}
    };
    
    stuArray[0].name = "Dog";

    cout << stuArray[0].name << stuArray[0].score <<endl;

    //結構體指針
    Student* p = &stuArray[0]; //定義
    int a = p -> score; //訪問 ->
    cout << a <<endl;
    system("pause");
}

四、結構體嵌套結構體

struct Student
{
      //成員列表
      string name;
      int age;
      int score;
}; 

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

五、結構體作為函數參數
結構體作為函數參數有值傳遞和地址傳遞兩種。

#include <iostream>
#include <stdlib.h>
using namespace std;

struct Student
{
      //成員列表
      string name;
      int age;
      int score;
}; 

//值傳遞
void printStudent(struct Student s)
{
    s.name = "Banana";
    cout << "name: " << s.name << "age: " << s.age << "score: " << s.score <<endl;
}

//地址傳遞
void printStudent2(struct Student* p)
{
    //p->name = "Banana";
    cout << "name: " << p->name << "age: " << p->age << "score: " << p->score << endl;
}

int main()
{
    struct Student s;
    s = {"Apple", 20, 89};
    printStudent(s);
    struct Student* p = &s;
    printStudent2(p);
    cout << "name: " << p->name << "age: " << p->age << "score: " << p->score << endl;
    system("pause");
}

六、結構體中使用const場景
用於防止誤操作。
因為值傳遞浪費空間，所以一般使用地址傳遞。
如果函數使用了地址傳遞，函數內操作會改變實參值，為了防止實參被亂修改，使用const。


用於設置只能讀不能寫。