C++ function overloading, calling "overloaded" function

Question

I have some code that looks like this:

// original function
size_t computeAverageRating(Movie m) { // take a movie object
    // compute average rating
}

// override original function
size_t computeAverageRating(size_t movieIndex) { // take the index of a movie
    getMovieObject(movieIndex);

    // call original function from here?
}

Is it possible to do what is being described in the comments without creating two separate methods with different names?

Yes. That's what overloaded functions are for. – R Sahu May 01 '14 at 16:20 — R Sahu, May 01 '14 at 16:20

score 4 · Accepted Answer · answered May 01 '14 at 16:18

4

Assuming getMovieObject() actually returns a Movie (although I'd change computeAverageRating() to take Movie &m to avoid copying the object):

size_t computeAverageRating(size_t movieIndex) { // take the index of a movie
  Movie m = getMovieObject(movieIndex);

  return computeAverageRating( m ) ;
}

Should do it.

answered May 01 '14 at 16:18

Paul Roub

36,322
27
84
93

2

You surely mean `const Movie &m`? – Mark Ingram May 01 '14 at 16:22
How can i call the overloaded method without compiler error, if I can't change it to `Movie& m` – vijayst Apr 13 '22 at 10:10

score 2 · Answer 2 · answered May 01 '14 at 16:20

2

Should work, its a good method so why do you want to look for another method?

size_t computeAverageRating(size_t movieIndex) {
    return computeAverageRating(getMovieObject(movieIndex));
}

answered May 01 '14 at 16:20

Shoaib

188
2
11

score 1 · Answer 3 · answered May 01 '14 at 16:18

What you have there is perfectly fine. The compiler will choose the best function based on the parameters, so for example:

size_t z;
Movie x;
size_t a = computeAverageRating(x);
size_t b = computeAverageRating(z);

Will get the average rating from the first function for a, then the second function for b.

score 0 · Answer 4 · answered May 01 '14 at 16:28

As per my knowledge, if the function is defined in the parent class, then you can't use the same function name with different parameter in child class without overriding the parent class function.

If you want to use then you have to either override the method defined in the parent class, or you need to put the declaration of new function definition in parent class.

ex:

class A
{
public:
    size_t computeAverageRating(Movie m) { // take a movie object
    // compute average rating
    }
};

class B:public A
{
    public:
    size_t computeAverageRating(Movie m)   //this is required
    {
        A::computeAverageRating(m);
    }
    size_t computeAverageRating(size_t movieIndex)
    {
           getMovieObject(movieIndex);
           //put your logic here
    }
};

or

class A
{
public:
    size_t computeAverageRating(Movie m) { // take a movie object
    // compute average rating
    }
    virtual size_t computeAverageRating(size_t movieIndex){};
};

class B:public A
{
    public:
    size_t computeAverageRating(size_t movieIndex)
    {
           getMovieObject(movieIndex);
           //put your logic here
    }
};

C++ function overloading, calling "overloaded" function

4 Answers4