为什么 const 成员必须在构造函数初始化器中而不是在其主体中初始化?
为什么声明为 const 的类成员必须在构造函数初始化器列表中初始化，而不是在构造函数体中?
Why must class members declared as const be initialized in the constructor initializer list rather than in the constructor body?
两者有什么区别?
推荐答案
在 C++ 中，当执行进入构造函数的主体时，对象被认为是完全初始化的.
In C++, an object is considered fully initialised when execution enters the body of the constructor.
你说:
"我想知道为什么 const 必须是在构造函数初始化器中初始化列表而不是正文?"
"i wanted to know why const must be intialized in constructor initializer list rather than in it's body ?."
您缺少的是 initialisation 发生在初始化列表中，而 assignment 发生在构造函数的主体中.逻辑步骤:
What you are missing is that initialisation happens in the initialisation list, and assignment happens in the body of the constructor. The steps in logic:
1) 一个 const 对象只能被初始化.
1) A const object can only be initialised.
2) 一个对象的所有成员都在初始化列表中初始化.即使您没有在此处显式初始化它们，编译器也会很乐意为您这样做:-)
2) An object has all of its members initialised in the initialisation list. Even if you do not explicitly initialise them there, the compiler will happily do so for you :-)
3) 因此，将 1) 和 2) 放在一起，const 成员只能在初始化时分配一个值，这发生在初始化列表期间.
3) Therefore, putting 1) and 2) together, a member which is const can only ever have a value assigned to it at initialisation, which happens during the initialisation list.
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