Question

此代码还有更多内容，但这是唯一不起作用的部分。无论我输入“Change”变量，它都只会给我第一个if语句的代码。我该如何解决这个问题？

std::cout << "Do you want to change any of this information? ";
std::string answer;
std::string x = "yes";
std::cin >> answer;
if(answer == x){
    std::cout << "What would you like to change:\nname(1), password(2), email(3), country(4), or cancel(5)?\nType the number of which you want to change: ";
    std::cin >> Change;
    if(Change = 1){
        std::cout << "Please type your new first name: ";
        std::cin >> FirstName;
        std::cout << "Middle Initial: ";
        std::cin >> MiddleInitial;
        std::cout << "Last Name: ";
        std::cin >> LastName;
        std::cout << "Thank you for signing up for Rowan's Demo Company!";
    }
    if(Change = 2){
        std::cout << "Please type your new password: ";
        std::cin >> Password;
        std::cout << "Thank you for signing up for Rowan's Demo Company!";
    }
    if(Change = 3){
        std::cout << "Please type your new email: ";
        std::cin >> Email;
        std::cout << "Thank you for signing up for Rowan's Demo Company!";
    }
    if(Change = 4){
        std::cout << "Please type your new country: ";
        std::cin >> Country;
        std::cout << "Thank you for signing up for Rowan's Demo Company!";
    }
    if(Change = 5){
        std::cout << "Thank you for signing up for Rowan's Demo Company!";
    }
}else{
    std::cout << "Thank you for signing up for Rowan's Demo Company!";
    }
return 0;

}

Answer 1

啊经典的错误。您无法使用=进行比较，而是必须使用==。单个=用于分配，它总是覆盖您的输入。

评估if语句if (Change = 1)的那一刻，Change得到值1，表达式进一步求值为true，它将执行{{1}的主体}}

请记住：if是作业，=是比较。

Answer 2

你在 if 中使用 = （赋值运算符）代替 == （比较运算符）进行条件表达式，你也应该在第一级嵌套中使用 if（）.. else if（）.. else ！（不是强制性的，但在这里是必要的！）您也可以在一些if语句中删除块（{.......}），因为其中只包含一个语句（为了简化它）！ 例如：

两者都会给出相同的结果！

 if(a==1)
    cout<<" you entered 1";
       // or
if(a==1) {
   cout<<"you entered 1";
}

输入不会影响if语句的使用

2 个答案: