Static member error in c++

Question

I am trying to define a static member pointer in C++. However I get a linker error. The error is

1>main.obj : error LNK2001: unresolved external symbol "public: static class Activity * * Solution::temp" (?temp@Solution@@2PAPAVActivity@@A)

1>Solution.obj : error LNK2001: unresolved external symbol "public: static class Activity * * Solution::temp" (?temp@Solution@@2PAPAVActivity@@A)

Code:

class Solution{

public:
    Activity **solution;

    Solution();
    Solution(Activity **list, bool direction);
    static Activity** temp;
};

Activity is another class. How can I solve this problem?

Answer 1

You have to add the definition:

Activity** Solution::temp = 0;

to the file that implements the class Solution.