Question

我遇到了这个错误，这是我在课堂上的代码并出现错误。

在没有类的情况下，数组工作正常，但是当我使用类时，出现了错误

class books{
    string author[20], title[20], publisher[20];
    float price[20];
    int stock_position[20];
    public: 
    books(){
        author[20] = {"author1", "author2", "author3", "author4", "author5", "author6", "author7", "author8", "author9","author10"};
        title[20] = {"book1", "book2", "book3", "book4", "book5", "book6", "book7", "book8", "book9", "book10"};
        publisher[20] = {"publisher1,", "publisher2", "publisher3", "publisher4", "publisher5", "publisher6", "publisher7", "publisher8", "publisher9", "publisher10",};
        price[20] = {12,23,34,45,56,67,67,78,45};
        stock_position[20] = {7,6,21,23,14,5,12,32,43,06};
    }
    input(string,string);
    find();
    buy();
    edit();
    display();  
};

错误：

[Warning] extended initializer lists only available with -std=c++11 or
-std=gnu++11 [Warning] extended initializer lists only available with  
-std=c++11 or -std=gnu++11 [Error] no match for 'operator=' (operand types 
 are 'std::string {aka std::basic_string<char>}' and
 '<brace-enclosed initializer list>')

Answer 1

那不是您初始化类成员的方式，而是分配。成员初始化仅在 ctor-initializer-list 中进行，而不会在构造函数主体中进行。

这也是您要实现的语法错误，并且在语义上是非法的。没有类似于 list-initialization 的“列表分配”语法。

author[20]不存在，有效的索引是从0到19。如果确实存在，它将仅引用一个string而不是整个数组。

使用 ctor-initializer-list 的正确语法如下（大括号初始化也需要C ++ 11， ctor-initializer-list中没有列表初始化在以前的C ++版本中）

class books
{
    std::string author[20], title[20], publisher[20];
    float price[20];
    int stock_position[20];
public: 
    books() 
        : author{"author1", "author2", "author3", "author4", "author5", "author6", "author7", "author8", "author9","author10"}
        , title{"book1", "book2", "book3", "book4", "book5", "book6", "book7", "book8", "book9", "book10"}
        , publisher{"publisher1,", "publisher2", "publisher3", "publisher4", "publisher5", "publisher6", "publisher7", "publisher8", "publisher9", "publisher10"}
        , price{12,23,34,45,56,67,67,78,45}
        , stock_position{7,6,21,23,14,5,12,32,43,06}
    {
    }
};

在C ++ 11之前，尽管为std::array和辅助函数提供了一种解决方法，但在为数组成员指定初始化程序时还是很不走运。

扩展的初始化程序列表仅适用于C ++中的-std = c ++ 11或-std = gnu ++ 11

1 个答案: