The Traits would be cool to standardise the behaviour and to mark it as such (implicit documentation), however, Traits cannot add instance/class variables IIUC, that limits what they can do (and would make it more than one step).
> On 19 Jan 2017, at 11:33, Cyril Ferlicot D. <cyril.ferli...@gmail.com> wrote: > > 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 >
