在bug中巩固C++

记录自己的各种报错，在错误中学习ing

结构体全局变量的声明与初始化问题

#include <iostream>
using namespace std;

//声明一个结构体Books
struct Book{
    string name;
    string author;
    string subject;
    int id;

    //构造函数
    Book(string name, string author, string subject, int id):name(name), author(author), subject(subject), id(id){
}
}book1,book2;

//打印
void printBookInfo(const Book& book)
{
    cout << "name: " << book.name << endl;
    cout << "author: " << book.author << endl;
    cout << "subject: " << book.subject << endl;
    cout << "ID: " << book.id << endl;
}

int main()
{
book1=Book("C++ Primer", "Bjarne Stroustrup", "Programming", 101);
book2=Book("C++ Primer Plus", "Bjarne Stroustrup", "Programming", 102);

printBookInfo(book1);
printBookInfo(book2);

return 0;
}

注意！这段代码主要问题在于 Book 结构体的成员变量book1和 book2 的初始化方式上。
book1 和 book2 是在全局范围内声明的变量，并且它们是结构体类型的实例，不能直接在声明之后使用赋值操作符进行初始化。
解决方法有两种
1.

在main函数外面声明并初始化

#include <iostream>
using namespace std;

// 声明一个结构体 Book
struct Book {
    string name;
    string author;
    string subject;
    int id;

    // 构造函数
    Book(string name, string author, string subject, int id) :
        name(name), author(author), subject(subject), id(id) {
    }
} book1("C++ Primer", "Bjarne Stroustrup", "Programming", 101),
  book2("C++ Primer Plus", "Bjarne Stroustrup", "Programming", 102);

// 打印函数
void printBookInfo(const Book& book) {
    cout << "name: " << book.name << endl;
    cout << "author: " << book.author << endl;
    cout << "subject: " << book.subject << endl;
    cout << "ID: " << book.id << endl;
}

int main() {
    // 已经在外部初始化了 book1 和 book2，直接调用打印函数即可
    printBookInfo(book1);
    printBookInfo(book2);

    return 0;
}

2.

在main函数中声明变量并初始化

#include <iostream>
using namespace std;

// 声明一个结构体 Book
struct Book {
    string name;
    string author;
    string subject;
    int id;

    // 构造函数
    Book(string name, string author, string subject, int id) :
        name(name), author(author), subject(subject), id(id) {
    }
};

// 打印函数
void printBookInfo(const Book& book) {
    cout << "name: " << book.name << endl;
    cout << "author: " << book.author << endl;
    cout << "subject: " << book.subject << endl;
    cout << "ID: " << book.id << endl;
}

int main() {
    // 使用构造函数初始化 book1 和 book2
    Book book1("C++ Primer", "Bjarne Stroustrup", "Programming", 101);
    Book book2("C++ Primer Plus", "Bjarne Stroustrup", "Programming", 102);

    // 调用打印函数
    printBookInfo(book1);
    printBookInfo(book2);

    return 0;
}