Question

Data is passed to a function “explicitly” whereas a method is “implicitly passed” to the object for which it was called.

Please could you explain the difference between these two ways of passing data? An example in java or c# would help.

Answer 1

The language Java and Python are good examples in illustrating this. In Python, the object is passed explicitly whenever a method of a class is defined:

class Example(object):

    def method(self, a, b):
        print a, b
        # The variable self can be used to access the current object

Here, the object self is passed explicitly as the first argument. This means that

e = Example()
e.method(3, 4)

is effectively the same as calling method(e, 3, 4) if method were a function.

However, in Java the first argument is not explicitly mentioned:

public class Example {
    public void method(int a, int b) {
        System.out.println(a + "  " + b);
        // The variable this can be used to access the current object
    } 
}

In Java, it would be:

Example e = Example();
e.method(3, 4);

The instance e is passed to method as well but the special variable this can be used to access it.

Of course, for functions each argument is passed explicitly because each argument is mentioned in both the function definition and where the function is called. If we define

def func(a, b, c):
    print a, b, c

then we can call it with func(1, 2, 3) which means all arguments are explicitly passed.