在对象构造后初始化const成员变量 [英] Initializing a const member variable after object construction

问题描述

我经常发现自己希望对象的成员变量可以是const，但是系统允许在构造后初始化该const变量。有一种机制可以让我做到这一点吗？

I often find myself wishing I could have an object's member variable be const, but that the system allowed initialization of that const variable after construction. Is there a mechanism that would allow me to do this?

为了澄清，下面是一个示例：

To clarify, here is an example:

class A
{
public:
    A(){}
    initialize(int x) { c = x; }
private:
    const int c;
}

我希望能够做到这一点。我在构造时没有此信息，因此不能简单地将初始化移到构造函数的初始化列表中。

I want to be able to do something like that. I don't have this information at construction, so I can't simply move initialization to the initialization list of the constructor.

推荐答案

不，您不能在构造后初始化const成员。

No, you cannot initialize const member after contruction.

但是请不要忘记，您可以在初始化列表中调用静态函数，因此在大多数情况下，您可以从初始值设定项列表中初始化成员

Do not forget, however, that you can call static functions in initializer list, so in most of cases you can initialize memebers from initializer list

class A
{
public:
    A(){}
    initialize(int x):c(computeC(x)) {}
private:
    const int c;
    static int computeC(int){/*...*/}
};

您还可以为该成员定义特殊的getter并使用它来访问成员。

You can also define special getter for that member and use it to access member.

class A
{
public:
    A(){}
    initialize(int x) { c_internal = x; }
private:
    const int& c() const { return c_internal; }
    int c_internal;
}

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