初始化静态变量时的语法错误 [英] Syntax error when initializing a static variable

问题描述

有两个类定义..

    class Dictionary
    {
    public:
        Dictionary();
        Dictionary(int i);
// ...
    };

和

    class Equation
    {
        static Dictionary operator_list(1);
// ...

    };

但问题是，每当我编译这个，我得到一个奇怪的错误信息

but the problem is, whenever I compile this, I get a weird error message

错误C2059：语法错误：'constant'

error C2059: syntax error : 'constant'

它编译好，当我使用默认构造函数在operator_list。

But it compiles well when I use the default constructor on operator_list.

推荐答案

在C ++中，不能结合声明和初始化。当不指定 operator_list 的构造函数参数时，不会调用其默认构造函数：您只需声明它。您还需要在相应的C ++文件中初始化它，如下所示：

In C++ you cannot combine declaration and initialization. When you do not specify constructor parameters of operator_list, you do not call its default constructor: you simply declare it. You need to also initialize it in the corresponding C++ file, like this:

Equation.h

Equation.h

class Equation {
    static Dictionary operator_list;
};

Equation.cpp：

Equation.cpp:

Dictionary Equation::operator_list(1);

注意CPP中没有 static 文件：它不是通过设计。编译器已经从声明中知道 operator_list 是静态的。

Note the absence of static in the CPP file: it is not there by design. The compiler already knows from the declaration that operator_list is static.

编辑：的积分和枚举类型：您可以在CPP文件中初始化它们，如上面的例子，或者你可以给他们一个值在标题。您仍然需要在C ++文件中定义该成员，但是在定义时不能给它一个值。

You have a choice with static constant members of integral and enumerated types: you can initialize them in the CPP file as in the example above, or you can give them a value in the header. You still need to define that member in your C++ file, but you must not give it a value at the definition time.

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