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Re: [Pharo-dev] About the singleton pattern

by Peter UhnÃ¡k

> > > Sometimes I use #new >> thatâs horrible! >> completely misleading >> > > I'm curious, if it is singleton, should you worry from outside about the > fact that it is a singleton? Shouldn't that be hidden from the user? > > nope. > new means new. > you are confusing your user if you send a new message and you receive an > already existing (aka not new) object. > the literature existing always recommend to use an specific method > (usually #instance or #uniqueInstance, in smalltalk.. who decided to use > #uniqueInstance as a convention). > Thanks for the explanation; I'm learning every day. :) Peter

April 8, 2015

Re: [Pharo-dev] About the singleton pattern

by Esteban Lorenzano

> On 08 Apr 2015, at 12:01, Peter UhnÃ¡k <i.uhnak(a)gmail.com> wrote: > > On Wed, Apr 8, 2015 at 11:52 AM, Esteban Lorenzano <estebanlm(a)gmail.com <mailto:estebanlm@gmail.com>> wrote: > > > On 08 Apr 2015, at 11:37, Yuriy Tymchuk <yuriy.tymchuk(a)me.com <mailto:yuriy.tymchuk@me.com>> wrote: > > > > Sometimes I use #new > thatâs horrible! > completely misleading > > I'm curious, if it is singleton, should you worry from outside about the fact that it is a singleton? Shouldn't that be hidden from the user? nope. new means new. you are confusing your user if you send a new message and you receive an already existing (aka not new) object. the literature existing always recommend to use an specific method (usually #instance or #uniqueInstance, in smalltalk.. who decided to use #uniqueInstance as a convention). Esteban > > Peter

April 8, 2015

Re: [Pharo-dev] About the singleton pattern

by Christophe Demarey

Le 8 avr. 2015 Ã 12:00, Esteban Lorenzano a Ã©crit : > I disagreeâ¦ probably they are not well used, but this is the meaning of each selector: > > - #uniqueInstance. As it saysâ¦ a pure singleton. > example: Author class>>#uniqueInstance. > Ideally, classes using this method also cancels #new. > > - #default. It gives you a default instance (as name says), but you can also create instances of it, for other uses. > example: RPackageOrganizer class>>#default. > > - #current. It gives you a singleton, but something that can change under certain circumstances, like a UI theme or a platform change. > example: OSPlatform class>>#current. You're right default does not have the same meaning. You have a default instance but you can create new ones. For #uniqueInstance and #current, the difference is subtle. You warn users that the singleton you get may change regarding the environment. > soâ¦ I do agree there are a lot of wrong uses there, that needs to be fixedâ¦ but each of the used selectors have a meaning, and a different meaning than the others. Yes, I did not get all the different meanings mostly because the right selector is not always used in the good context. On the other side, I wonder about the #uniqueInstance selector. Are there a lot of situations where you absolutely do not want another instance of this class (even for test purposes)? > cheers, > Esteban > > >> On 08 Apr 2015, at 11:31, Christophe Demarey <Christophe.Demarey(a)inria.fr> wrote: >> >> Hi, >> >> We use quite often the singleton pattern but when I need to use one, I always need to ask myself "What is the selector to get this singleton?". >> We use either aClass>>current, aClass>>default or aClass>>uniqueInstance. >> Could we agree on the selector to use and update existing code? >> >> To get a quick overview, I searched about these methods in a Pharo4 image and get these results: >> ((SystemNavigation default allImplementorsOf: #default) select: #isMetaSide) size. "45" >> ((SystemNavigation default allImplementorsOf: #current) select: #isMetaSide) size. "40" >> ((SystemNavigation default allImplementorsOf: #uniqueInstance) select: #isMetaSide) size. "19" >> >> Your opinion? >> >> Christophe. > >

April 8, 2015

Re: [Pharo-dev] About the singleton pattern

by Benoit St-Jean

We should also consider the cases of globals like Processor and Transcript. Â ----------------- BenoÃ®t St-Jean Yahoo! Messenger: bstjean Twitter: @BenLeChialeux Pinterest: benoitstjean IRC: lamneth Blogue: endormitoire.wordpress.com "A standpoint is an intellectual horizon of radius zero".Â (A. Einstein) From: Christophe Demarey <Christophe.Demarey(a)inria.fr> To: Pharo Development List <pharo-dev(a)lists.pharo.org> Sent: Wednesday, April 8, 2015 5:31 AM Subject: [Pharo-dev] About the singleton pattern Hi, We use quite often the singleton pattern but when I need to use one, I always need to ask myself "What is the selector to get this singleton?". We use either aClass>>current, aClass>>default or aClass>>uniqueInstance. Could we agree on the selector to use and update existing code? To get a quick overview, IÂ searched about these methods in a Pharo4Â image and get these results: ((SystemNavigation default allImplementorsOf: #default) select: #isMetaSide) size. "45" ((SystemNavigation default allImplementorsOf: #current) select: #isMetaSide) size.Â "40" ((SystemNavigation default allImplementorsOf: #uniqueInstance) select: #isMetaSide) size.Â "19" Your opinion? Christophe.

April 8, 2015

Re: [Pharo-dev] About the singleton pattern

by Norbert Hartl

> Am 08.04.2015 um 12:00 schrieb Esteban Lorenzano <estebanlm(a)gmail.com>: > > I disagreeâ¦ probably they are not well used, but this is the meaning of each selector: > > - #uniqueInstance. As it saysâ¦ a pure singleton. > example: Author class>>#uniqueInstance. > Ideally, classes using this method also cancels #new. > > - #default. It gives you a default instance (as name says), but you can also create instances of it, for other uses. > example: RPackageOrganizer class>>#default. > > - #current. It gives you a singleton, but something that can change under certain circumstances, like a UI theme or a platform change. > example: OSPlatform class>>#current. > > soâ¦ I do agree there are a lot of wrong uses there, that needs to be fixedâ¦ but each of the used selectors have a meaning, and a different meaning than the others. > +1 Norbert > >> On 08 Apr 2015, at 11:31, Christophe Demarey <Christophe.Demarey(a)inria.fr> wrote: >> >> Hi, >> >> We use quite often the singleton pattern but when I need to use one, I always need to ask myself "What is the selector to get this singleton?". >> We use either aClass>>current, aClass>>default or aClass>>uniqueInstance. >> Could we agree on the selector to use and update existing code? >> >> To get a quick overview, I searched about these methods in a Pharo4 image and get these results: >> ((SystemNavigation default allImplementorsOf: #default) select: #isMetaSide) size. "45" >> ((SystemNavigation default allImplementorsOf: #current) select: #isMetaSide) size. "40" >> ((SystemNavigation default allImplementorsOf: #uniqueInstance) select: #isMetaSide) size. "19" >> >> Your opinion? >> >> Christophe. > >

April 8, 2015

Re: [Pharo-dev] About the singleton pattern

by Peter UhnÃ¡k

On Wed, Apr 8, 2015 at 11:52 AM, Esteban Lorenzano <estebanlm(a)gmail.com> wrote: > > > On 08 Apr 2015, at 11:37, Yuriy Tymchuk <yuriy.tymchuk(a)me.com> wrote: > > > > Sometimes I use #new > thatâs horrible! > completely misleading > I'm curious, if it is singleton, should you worry from outside about the fact that it is a singleton? Shouldn't that be hidden from the user? Peter

April 8, 2015

Re: [Pharo-dev] About the singleton pattern

by Esteban Lorenzano

I disagreeâ¦ probably they are not well used, but this is the meaning of each selector: - #uniqueInstance. As it saysâ¦ a pure singleton. example: Author class>>#uniqueInstance. Ideally, classes using this method also cancels #new. - #default. It gives you a default instance (as name says), but you can also create instances of it, for other uses. example: RPackageOrganizer class>>#default. - #current. It gives you a singleton, but something that can change under certain circumstances, like a UI theme or a platform change. example: OSPlatform class>>#current. soâ¦ I do agree there are a lot of wrong uses there, that needs to be fixedâ¦ but each of the used selectors have a meaning, and a different meaning than the others. cheers, Esteban > On 08 Apr 2015, at 11:31, Christophe Demarey <Christophe.Demarey(a)inria.fr> wrote: > > Hi, > > We use quite often the singleton pattern but when I need to use one, I always need to ask myself "What is the selector to get this singleton?". > We use either aClass>>current, aClass>>default or aClass>>uniqueInstance. > Could we agree on the selector to use and update existing code? > > To get a quick overview, I searched about these methods in a Pharo4 image and get these results: > ((SystemNavigation default allImplementorsOf: #default) select: #isMetaSide) size. "45" > ((SystemNavigation default allImplementorsOf: #current) select: #isMetaSide) size. "40" > ((SystemNavigation default allImplementorsOf: #uniqueInstance) select: #isMetaSide) size. "19" > > Your opinion? > > Christophe.

April 8, 2015

Re: [Pharo-dev] About the singleton pattern

by Peter UhnÃ¡k

Also ((SystemNavigation default allImplementorsOf: #instance) select: #isMetaSide) size. "10" ((SystemNavigation default allImplementorsOf: #singleton) select: #isMetaSide) size. "1" This reminded me of this https://twitter.com/ID_AA_Carmack/status/575788622554628096 considering we already use a/an for parameters, this can be quite fitting. But some consensus would be niceâ¦ personally I don't really like that I have to think about the fact that it is a singleton, so The* + #new sounds interesting. Otherwise to me #current sounds much more fitting than #default (in fact I would expect them return different things if #current: has been used). Peter On Wed, Apr 8, 2015 at 11:37 AM, Yuriy Tymchuk <yuriy.tymchuk(a)me.com> wrote: > Sometimes I use #new > > > On 08 Apr 2015, at 11:31, Christophe Demarey < > Christophe.Demarey(a)inria.fr> wrote: > > > > Hi, > > > > We use quite often the singleton pattern but when I need to use one, I > always need to ask myself "What is the selector to get this singleton?". > > We use either aClass>>current, aClass>>default or aClass>>uniqueInstance. > > Could we agree on the selector to use and update existing code? > > > > To get a quick overview, I searched about these methods in a Pharo4 > image and get these results: > > ((SystemNavigation default allImplementorsOf: #default) select: > #isMetaSide) size. "45" > > ((SystemNavigation default allImplementorsOf: #current) select: > #isMetaSide) size. "40" > > ((SystemNavigation default allImplementorsOf: #uniqueInstance) select: > #isMetaSide) size. "19" > > > > Your opinion? > > > > Christophe. > > >

April 8, 2015

Re: [Pharo-dev] About the singleton pattern

by Esteban Lorenzano

> On 08 Apr 2015, at 11:37, Yuriy Tymchuk <yuriy.tymchuk(a)me.com> wrote: > > Sometimes I use #new thatâs horrible! completely misleading > >> On 08 Apr 2015, at 11:31, Christophe Demarey <Christophe.Demarey(a)inria.fr> wrote: >> >> Hi, >> >> We use quite often the singleton pattern but when I need to use one, I always need to ask myself "What is the selector to get this singleton?". >> We use either aClass>>current, aClass>>default or aClass>>uniqueInstance. >> Could we agree on the selector to use and update existing code? >> >> To get a quick overview, I searched about these methods in a Pharo4 image and get these results: >> ((SystemNavigation default allImplementorsOf: #default) select: #isMetaSide) size. "45" >> ((SystemNavigation default allImplementorsOf: #current) select: #isMetaSide) size. "40" >> ((SystemNavigation default allImplementorsOf: #uniqueInstance) select: #isMetaSide) size. "19" >> >> Your opinion? >> >> Christophe. > >

April 8, 2015

Re: [Pharo-dev] About the singleton pattern

by Yuriy Tymchuk

Sometimes I use #new > On 08 Apr 2015, at 11:31, Christophe Demarey <Christophe.Demarey(a)inria.fr> wrote: > > Hi, > > We use quite often the singleton pattern but when I need to use one, I always need to ask myself "What is the selector to get this singleton?". > We use either aClass>>current, aClass>>default or aClass>>uniqueInstance. > Could we agree on the selector to use and update existing code? > > To get a quick overview, I searched about these methods in a Pharo4 image and get these results: > ((SystemNavigation default allImplementorsOf: #default) select: #isMetaSide) size. "45" > ((SystemNavigation default allImplementorsOf: #current) select: #isMetaSide) size. "40" > ((SystemNavigation default allImplementorsOf: #uniqueInstance) select: #isMetaSide) size. "19" > > Your opinion? > > Christophe.

April 8, 2015