An example code concerning inheritance of object messages:
Rebol[
Purpose: "Demonstrate non-copied object messages."
]
;Define the object without messages
a: make object! [
num: 1
;Other non-message attributes here...
messages: none
]
;Now define the messages, common for all descendants.
;These are created only once
;and aren't copied as long as
;you don't change anything for a descendant...
a/messages: make object! [
;An example message
get-num: func [
;every message must have access to object to which it has been
sent...
obj [object!]
;the room for message parameters...
param
] [
;This is the body of the message
obj/num
]
;Other messages here...
]
;Function to send messages, shouldn't be changed
sm: func [obj [object!] 'message [word!] param [block!]] [
do in obj/messages message obj param
]
;Now you can use the code like this:
>> sm a get-num []
== 1
>> b: make a [num: num + 1]
>> sm b get-num []
== 2
- Ladislav
