在非静态函数中比较静态和非静态整数 [英] Compare static and non-static integer in non-static function

问题描述

我有一个静态变量，我用作计数器和非静态版本的变量，我用来保存计数器的值在某些事件。下面是一些代码：

I have a static variable that I use as a counter and a non-static version of the variable that I use to save the value of the counter at certain events. Here is some code:

头文件：

static int UndoID;
int UndoRedoID;

void SetUnsavedChanges();

类：

我尝试这样的类：

UndoRedoID = UndoID;

我尝试过其他的操作：

UndoRedoID = myClass:UndoID;

比较示例：

void myClass::SetUnsavedChanges()
{
    if (UndoRedoID != UndoID)
    {
        cout << "Unsaved";
    }
    else
    {
        cout << "Saved";
    }
}

这导致我得到链接错误， p>

This causes me to get linking errors like:

Undefined symbols:
  "myClass::UndoID", referenced from:
    myClass::SetUnsavedChanges()       in myClass_lib.a(myClass.o)
    ...

感谢您的帮助： ）

推荐答案

您需要定义静态成员数据， >

You need to define the static member data, outside the class as:

//this should be done in .cpp file
int myClass::UndoID;

让我添加一个例子：

//X.h
class X
{
   static int s; //declaration of static member
};

然后在 X.cpp 应该这样做：

//X.cpp
#include "X.h"

int X::s; //definition of the static member

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