Monkey Documentation

Keyword Extends

Declares that class definition inherits a parent class.

Syntax

Class Identifier [ < Parameters > ] [ Extends Class ] [ Implements Interfaces ] [ Final ]
' Declarations...
End [ Class ]

Description

The Extends keyword allows a class to 'extend' a parent class, thereby inheriting all of its fields, methods, functions, globals and constants.

This new class can add its own fields, methods, etc, but can also over-ride the existing fields, methods and so on by redefining them.

See also

Class | Super
Language reference

Example

Here we have three classes:

  • a base class, Animal, with an 'x' field, a 'legs' field and a 'Move' method;
  • the Dog class 'extends' the Animal class, inheriting the x and legs fields and adding its own 'Bark' method;
  • the Fly class also extends the Animal class, but over-rides the legs field and Move method, while adding a 'y' field and a 'Buzz' method.

Class Animal

    Field x
    Field legs = 4

    Method Move ()
        x = x + 1
    End

End

Class Dog Extends Animal

    Method Bark ()
        Print "Woof"
    End

End

Class Fly Extends Animal

    Field legs = 6
    Field y

    Method Move ()
        x = Rnd (-4, 4)
        y = Rnd (-4, 4)
    End

    Method Buzz ()
        Print "ZzzzZZZzzzzzZZZZ..."
    End

End