在C ++类或结构上声明只读变量

问题描述

我从C＃进入C ++，而const-correctness对我来说仍然是新事物。在C＃中，我可以声明这样的属性：

I'm coming to C++ from C# and const-correctness is still new to me. In C# I could declare a property like this:

class Type
{
    public readonly int x;
    public Type(int y)
    {
        x = y;
    }
}

这将确保x仅在初始化期间设置。我想在C ++中做类似的事情。我能想到的最好的方法是：

This would ensure that x was only set during initialization. I would like to do something similar in C++. The best I can come up with though is:

class Type
{
private:
    int _x;
public:
    Type(int y) { _x = y; }
    int get_x() { return _x; }
};

是否有更好的方法？甚至更好：我可以使用结构体来做到这一点吗？我想到的类型实际上只是数据的集合，没有逻辑，因此如果我可以保证仅在初始化期间设置其值，则结构会更好。

Is there a better way to do this? Even better: Can I do this with a struct? The type I have in mind is really just a collection of data, with no logic, so a struct would be better if I could guarantee that its values are set only during initialization.

推荐答案

有一个 const 修饰符：

class Type
{
private:
   const int _x;
   int j;

public:
    Type(int y):_x(y) { j = 5; }
    int get_x() { return _x; }
    // disable changing the object through assignment
    Type& operator=(const Type&) = delete;
};

请注意，您需要在构造函数初始化列表中初始化常量。您还可以在构造函数主体中初始化其他变量。

Note that you need to initialize constant in the constructor initialization list. Other variables you can also initialize in the constructor body.

关于第二个问题，是的，您可以执行以下操作：

About your second question, yes, you can do something like this:

   struct Type
   {
      const int x;
      const int y;

      Type(int vx, int vy): x(vx), y(vy){}
      // disable changing the object through assignment
      Type& operator=(const Type&) = delete;
   };

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