[Cuis] #when:send:to:

[Dan Norton]

Hello Everyone,

The following repo contains before and after examples of replacing the Dependency 
Mechanism with the Observer Pattern:

	https://github.com/dhnorton/Cuis-Smalltalk-light

Please take a look at this and tell me what needs to change. I'm trying to supply an example 
of the Observer Pattern so that others might use #when:send:to: with less difficulty than I 
experienced. There may be better examples but I picked one from the Blue Book.

It seems that #when:send:to: is necessary but not sufficient as a replacement for the 
Dependency Mechanism. In this example, it replaced #addDependent:, not #changed or 
#update and I am still not comfortable with how to choose the parameters. This may be an 
example of the difficulty in explaining the obvious, I'm not sure :-)

The #changed method was replaced with #triggerEvent: with a symbol argument which is 
referred to in one of the arguments of #when:send:to: and that's the only constraint AFAICT.

The #update: method was retained, as a convenience; it also needs to agree with one of the 
arguments of #when:send:to: and could have been different.

Please tell me if any of this is wrong. Thanks.

 - Dan