CODEWITHSUNDEEP
c++objectoopstatic
loveofprogramming
loveofprogramming

Reputation: 95

Defining a static member

Consider the following code:

#include <iostream >
using namespace std;

class A
{
private:
    int x;
public:
    A(int _x)  {  x = _x; }
    int get()  { return x; }
};

class B
{
    static A a;
public:
   static int get()
   {  return a.get(); }
};

A B::a(0);

int main(void)
{
    B b;
    cout << b.get();
    return 0;
}

My book says:

If we do not use the line of code A B::a(0),there is a compiler error because static member a is not defined in B. To fix the error, we need to explicitly define a.

However, I thought of initializing object a as static A a(0); but it gives me a compiler error. Can someone explain why I can't initialize object a in the manner I described, and why it is necessary to initialize it as they had given it in book.

Upvotes: 1

Views: 79

Answers (1)

Ted Lyngmo
Ted Lyngmo

Reputation: 117298

If you want to define a inline, you need to inline it, which is possible from C++17:

class B {
    inline static A a{0};    // or   inline static A a = 0;
public:
    static int get() { return a.get(); }
};

Demo

Upvotes: 1

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