对静态变量c ++的未定义引用

问题描述

您好，我在下面的代码中得到未定义的引用错误：

Hi i am getting undefined reference error in the following code:

class Helloworld{
  public:
     static int x;
     void foo();
};
void Helloworld::foo(){
     Helloworld::x = 10;
};

我不想要一个 static code> foo（）函数。如何在类的非 - static 方法中访问类的 static 变量？

I don't want a static foo() function. How can I access static variable of a class in non-static method of a class?

推荐答案

好， foo c $ c>是不是在您的类中静态，并且 需要使它 static 访问 static 您类的变量。

Well, foo() is not static in your class, and you do not need to make it static in order to access static variables of your class.

您需要做的只是提供一个 / em>为你的静态成员变量：

What you need to do is simply to provide a definition for your static member variable:

class Helloworld {
  public:
     static int x;
     void foo();
};

int Helloworld::x = 0; // Or whatever is the most appropriate value
                       // for initializing x. Notice, that the
                       // initializer is not required: if absent,
                       // x will be zero-initialized.

void Helloworld::foo() {
     Helloworld::x = 10;
};

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