Inheritance of IDL Interfaces

IDL supports inheritance of interfaces. An IDL interface can inherit all the elements of one or more other interfaces.

For example, the following IDL definition illustrates two interfaces, called CheckingAccount and SavingsAccount, that inherit from interface Account:

    module Finance { 
      interface Account { 
        ... 
      }; 
      interface CheckingAccount : Account { 
        readonly attribute overdraftLimit; 
        boolean orderChequeBook (); 
      }; 
      interface SavingsAccount : Account { 
        float calculateInterest (); 
      }; 
    }; 

• Interfaces CheckingAccount and SavingsAccount implicitly include all elements of interface Account.
• An object that implements CheckingAccount can accept invocations on any of the attributes and operations of this interface, and on any of the elements of interface Account.
• However, a CheckingAccount object may provide different implementations of the elements of interface Account to an object that implements Account only.
• The following IDL definition shows how to define an interface that inherits both CheckingAccount and SavingsAccount:

  
      module Finance { 
        interface Account { 
          ... 
        }; 
        interface CheckingAccount : Account { 
          ... 
        }; 
        interface SavingsAccount : Account { 
          ... 
        }; 
        interface PremiumAccount : CheckingAccount, SavingsAccount { 
        }; 
      }; 
  

  Interface PremiumAccount is an example of multiple inheritance in IDL.
• An interface can inherit from two interfaces that include a constant, type, or exception definition of the same name. But then you must fully scope that name when using that constant, type, or exception.
• An interface cannot inherit from two interfaces that include operations or attributes that have the same name.