On 19/01/2017 11:23, Siemen Baader wrote: > Is there a trait to quickly create singletons in Pharo, along the way of > the Ruby Singleton mixin? > > https://ruby-doc.org/stdlib-1.9.3/libdoc/singleton/rdoc/Singleton.html > > (and ideally also observer/observable, which I am going to need next..) > > -- Siemen
Hi!
Singleton in Smalltalk are really easy so there is no Trait.
You just need a class variable #UniqueInstance and those methods:
current
"Can also be named #default or #instance"
^ UniqueInstance
ifNil: [ UniqueInstance := self basicNew; initialize; yourself ]
new
^ self error: 'I am a Singleton. Use current to get my instance or
reset my instance with a new project. Maybe explain why there is a
Singleton because we should avoid them if possible.'
Now for the observer pattern you have the Announcement framework in Pharo.
I don't really have the time to explain but I think there is some doc on
internet and on the help browser of Pharo. I found this:
http://pharo.gemtalksystems.com/book/LanguageAndLibraries/announcements/
(I did not read it so I don't know what it's worth)
--
Cyril Ferlicot
http://www.synectique.eu
2 rue Jacques Prévert 01,
59650 Villeneuve d'ascq France
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