使用方法
在头文件中声明变量,在cpp文件中使用。
声明时使用extern关键字 告诉编译器去其他文件中寻找
示例代码
test.h
#ifndef TEST_H
#define TEST_H
int global_v;
#endif
test.cpp
#include <iostream>
#include "test.h"
using namespace std;
int global_v = 1;
void modify()
{
global_v++;
cout << "in test, value increases to " << global_v << endl;
}
main.cpp
#include <iostream>
#include "test.h"
using namespace std;
extern int global_v;
int main()
{
cout << "in main, value is " << global_v << " before modify" << endl;
modify();
cout << "in main, value is " << global_v << " after modify" << endl;
return 0;
}