CODEWITHSUNDEEP
c++sqlitec++11
user4815896
user4815896

Reputation:

How to make a non-static callback in c++ for sqlite?

I have some code that gets data from a database and stores it in a struct but I get an error "reference to non-static member function must be called".

class ScoreManagement {

private:
    int callback(void *NotUsed, int argc, char **argv, 
                char **azColName) {

        NotUsed = 0;


        playerRecords[player_number].name =  argv[1] ? argv[1] : "NULL";

        player_number++
        return 0;
    }

    void showScore(string userinput) {
        string query = "SELECT * FROM SCORES"; 

        sqlite3_exec(DB, query.c_str(), callback, NULL, NULL);

    }
};

Upvotes: 0

Views: 896

Answers (1)

Jeremy Friesner
Jeremy Friesner

Reputation: 73121

The trick is to a create a static "helper" method, and use the void-pointer argument provided in the callback-signature to pass a pointer to your object into that method. Then the static helper method can use that pointer to call the non-static method:

class ScoreManagement {
public:
   static int callback(void *objPtr, int argc, char **argv, char **azColName) {
      return ((ScoreManagement *)objPtr)->callbackAux(argc, argv, azColName);
   }

private:
   int callbackAux(int argc, char ** argv, char ** azColName) {
      playerRecords[player_number].name =  argv[1] ? argv[1] : "NULL";
      player_number++;
      return 0;
   }
};

[...]

// Note that you must pass in a pointer to your `ScoreManagement` object
// as an argument here, so that it will be passed in to `callback()`
sqlite3_exec(DB, query.c_str(), ScoreManagement::callback, &myScoreManagementObject, NULL);

Upvotes: 4

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