Changing the Search Order for Methods

When composing a message, you can change the default search order for methods by doing both of the following:

Making the receiver object the sender object. You usually do this by specifying the special variable SELF. SELF holds the value of the object in which a method is running.
Specifying a colon and a starting scope after the message name. The starting scope is a variable or environment symbol that identifies the scope object to use as the method search starting point. This scope object can be:
- A direct superclass of the class that defines the active method
- The object itself (for example, the value of the variable SELF), if you used SETMETHOD to add methods to the object.
  
  The scope variable is usually the special variable SUPER, but it can be any environment symbol or variable name whose value is a valid superclass.

In A Sample Program Using Directives , an Account subclass of the Object superclass is created. It defines a TYPE method for Account, and creates the Savings subclass of Account.. The example defines a TYPE method for the Savings subclass, as follows:

SUBCLASS Option

::class Savings subclass Account

::method "TYPE"

return "a savings account"

To change the search order so Rexx searches for TYPE in the Account rather than Savings subclass, enter this instead:

Changing the Subclass Method Search Order

::method "TYPE"

return self~type:super -- returns the result of invoking the TYPE method of the superclass

When you create an asav instance of the Savings subclass and send a TYPE message to asav:

say asav~type

Rexx displays:

an account

rather than:

a savings account

because Rexx searches for TYPE in the Account class first.