Interfaces

An interface is a list of instance methods specifying names and signatures but without implementation.

Context:

    Program Structure
        Types

interface-specification

interface-header

interface-member

Example

*> Interface definition
interface-id IAlarmClock.
  ...
end interface.
 
*> Inheriting an interface 
interface-id IAlarmClock inherits type IClock.
  ...
end interface.
 
*> Interface implementation
class-id WristWatch implements type IAlarmClock, type ITimer.
   ...
end class.

About Interfaces

An interface is a list of instance methods specifying names and signatures but without implementation.

When a program declares that it implements a particular interface this means that the program is required to have implementations for all the methods defined in the interface. To implement an interface you use the IMPLEMENTS phrase of the OBJECT clause in a class definition to declare that a program provides an implementation for the specified interface. You can also declare an object reference to this interface type.