Question

成员变量或字段与全局变量之间有什么区别？概念是否相同？

Answer 1

成员变量在类的范围内声明。除非它是静态的，否则该类的每个对象都会有一个不同的变量副本。

全局变量在任何类的范围之外声明，可以在任何函数中使用。程序中只有一份副本。

示例代码

#include <iostream>

using std::cout;
using std::endl;

const int global_var = 1;   // The definition of the global variable.

struct example_t {
  public:

  static int static_member_var; // A static member variable.
  const static int const_static_member_var; // These are just declarations.

  int member_var;                   // A non-static member variable.
  // Every object of this type will have its own member_var, while all
  // objects of this type will share their static members.
};

int example_t::static_member_var = 0;
const int example_t::const_static_member_var = global_var;
// We can use global_var here.  Both of these exist only once in the
// program, and must have one definition.  Outside the scope where we
// declared these, we must give their scope to refer to them.

    int main(void)
    {
      example_t a, b;   // Two different example_t structs.

      a.member_var = 2;
      b.member_var = 3; // These are different.

      a.static_member_var = 5;
      // This is another way to refer to it.  Because b has the same variable, it
      // changes it for both.

      // We can use global_var from main(), too.
      cout << "global_var is " << global_var
           << ", example_t::const_static_member_var is " << example_t::const_static_member_var
           << ", b.static_member_var is " << b.static_member_var
           << ", a.member_var is " << a.member_var
           << " and b.member_var is " << b.member_var
           << "."  << endl;

      return 0;
    }

＆＃34;成员变量＆＃34;之间的差异或＆＃34;字段＆＃34;和一个＆＃34;全局变量＆＃34;

1 个答案:

示例代码