:answer

Type:	-	message selector
Source:	-	xlobj.c

Syntax

(send class :answer message args code)

class - an existing class
message - the message symbol
args - formal argument list to the 'msg' method of the same form as a lambda argument list
code - a list containing the method code
returns - the class object

Description

The ':answer' message selector adds or changes a method in the specified class. This method consists of the 'message' selector symbol, the 'arg' formal argument list and the executable 'code' associated with the message.

Examples

(setq myclass (send class :new '(var)))              ; create MYCLASS with VAR
(send myclass :answer :isnew '()                     ; set up initialization
                             '((setq var nil) self))
(send myclass :answer :set-it '(value)               ; create :SET-IT message
                              '((setq var value)))    
(send myclass :answer :mine '()                      ; create :MINE message
                            '((print "hi there")))          
(setq my-obj (send myclass :new))                    ; create MY-OBJ of MYCLASS
(send my-obj :set-it 5)                              ; VAR is set to 5
(send my-obj :mine)                                  ; prints  "hi there"

Note: When you define a message in a class , the message is only valid for instances of the class or its sub-classes. You will get an error if you try to send the message to the class where it was first defined. If you wish to add a message to the class , you need to define it in the super-class of the class.

Message structure: The normal XLISP convention for a message is to have a valid symbol preceeded by a colon like :isnew or ':my-message'. However, it is possible to define a message that is a symbol without a colon, but this makes the code less readable.

See the :answer message selector in the XLISP 2.0 manual.

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