在 C++ 类中初始化静态变量?

问题描述

我注意到类中的某些函数实际上并未访问该对象，因此我将它们设为 static.然后编译器告诉我他们访问的所有变量也必须是静态的——嗯，到目前为止还可以理解.我有一堆字符串变量，例如

I have noticed that some of my functions in a class are actually not accessing the object, so I made them static. Then the compiler told me that all variables they access must also be static – well, quite understandable so far. I have a bunch of string variables such as

string RE_ANY = "([^\n]*)";
string RE_ANY_RELUCTANT = "([^\n]*?)";

等等.然后我将它们全部设为 static const 因为它们永远不会改变.但是，我的程序只有在我将它们移出类时才会编译:否则，MSVC++2010 会抱怨只有静态常量整数变量可以在类中初始化".

and so on in the class. I have then made them all static const because they never change. However, my program only compiles if I move them out of the class: Otherwise, MSVC++2010 complains "Only static constant integral variables may be initialized within a class".

那很不幸.有解决方法吗?我想把他们留在他们所属的班级里.

Well that's unfortunate. Is there a workaround? I would like to leave them inside the class they belong to.

推荐答案

它们不能在类内部初始化，但可以在类外部初始化，在源文件中:

They can't be initialised inside the class, but they can be initialised outside the class, in a source file:

// inside the class
class Thing {
    static string RE_ANY;
    static string RE_ANY_RELUCTANT;
};

// in the source file
string Thing::RE_ANY = "([^\n]*)";
string Thing::RE_ANY_RELUCTANT = "([^\n]*?)";

更新

我刚刚注意到你问题的第一行 - 你不想想让这些函数static，你想让它们const.使它们 static 意味着它们不再与对象相关联(因此它们不能访问任何非静态成员)，并使数据静态意味着它将与此类型的所有对象共享.这很可能不是您想要的.使它们 const 仅仅意味着它们不能修改任何成员，但仍然可以访问它们.