CODEWITHSUNDEEP
c++pointers
gath
gath

Reputation: 25492

How to call pointer member function inside a class definition?

How do I call a pointer member function within a class definition? My code:

//Myclass.h

struct Booking{
  int src;
  int dest;
  int pos;
};

class MyClass{
public:
    void ExecutePlan();
private:
    struct FlightPlan{
      string name;
      vector<Booking> bookings
    };

    typedef FlightPlan FP;
    FP firstplan;
    FP secondplan;
    void FirstPlan(Booking& book);
    void SecondPlan(Booking& book);
    void Execute(FP& fplan, void (MyClass::*mptr)(Booking& book));
};

// Myclass.cpp
void MyClass::FirstPlan(Booking& book){
// do something with booking
}

void MyClass::SecondPlan(Booking& book){
// do something with booking
}

void MyClass::Execute(FP& fplan, void(MyClass::*mptr)(const FlightPlan& fp)){
    for (int i=0; i<.fplan.bookings.size(); i++){
        cout << "Executing Plan: "<< fplan.name << endl;

       // Problematic line ...
        mptr(bookings[i]);   // <----- can't compile with this
    }
}

void MyClass::Execute(){
// is this the correct design to call this member functions ???

   Execute(firstplan, &MyClass::FirstPlan)   
   Execute(secondplan, &MyClass::SecondPlan)   
}

How can i structure the Execute Function to receive a member function as a pointer?

Pls: Am a newbie in C++, maybe the design is weird!!

Paul

Upvotes: 0

Views: 343

Answers (2)

Mike Seymour
Mike Seymour

Reputation: 254751

How to call pointer member function inside a class definition?

Unlike member names, member pointers aren't implicitly applied to this. You have to be explicit:

(this->*mptr)(fplan.bookings[i]);

is this the correct design to call this member functions ???

Apart from a few obvious errors (such as missing ; here and there, saying const FlightPlan& where you mean Booking& in the definition of Execute), the rest of the code looks fine. Specifically

Execute(firstplan, &MyClass::FirstPlan)   
Execute(secondplan, &MyClass::SecondPlan)

is the correct syntax for obtaining the member-function pointers.

Upvotes: 3

Wojtek Surowka
Wojtek Surowka

Reputation: 21003

The operator to call a member function pointer is ->*. Since you want to call it on this object, you need to use

(this->*mptr)(bookings[i]);

Upvotes: 1

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