初始化禁止复制的成员类 [英] Initialize member class that prohibits copy

问题描述

我有一个成员变量，该成员变量是禁止复制的类(删除了复制赋值运算符).我想进行一些检查以确定将成员初始化为什么，因此我需要在构造函数中而不是在初始化列表中进行此操作.似乎成员变量m在进入MyClass的构造函数之前已经使用默认的构造函数进行了初始化，那么该构造函数的意义是什么...对不起c ++ rant.

I have a member variable that is a class that prohibits copying (copy assignment operator is deleted). I want to make some checks to determine what to initiate the member to, thus I need to do this inside the constructor and not in and initializer list. It seem the member variable m is already initialed with the default constructor before entering the constructor of MyClass, then what is the point of the constructor... sorry for c++ rant.

简单的例子:

class MyClass {
    NonCopy m;
    MyClass() {
        // Complex checks
        if(success) {
            m("success");
        else {
            m("failure");
        }

    }

我看到的选项是:

• 依赖于m的动态分配
• 禁止复制m的要求

推荐答案

只要该类具有有效的副本或move构造函数，或者您正在使用C ++ 17 +，就可以创建一个执行逻辑的辅助函数.然后返回正确的对象.然后，您可以使用它来初始化您的成员.看起来像

As long as the class has a valid copy or move constructor, or you are using C++17+, you can make a helper function that does the logic and then returns the correct object. You then use that to initialize your member. That would look like

class MyClass {
    NonCopy m;
    static NonCopy initialize_noncopy()
    {
        // Complex checks
        if(success) {
            return NonCopy("success");
        else {
            return NonCopy("faulure");
        }
    }
public:
    MyClass() : m(initialize_noncopy()) { }
};

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