canonical way to convert Symbol into Class (retrieve class by its name)
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Re: canonical way to convert Symbol into Class (retrieve class by its name)
 
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2018-02-13 10:25 GMT+01:00 Marcus Denker <[hidden email]>:
I really like this idea. We just need to represent undefined variable value as special object instead of nil.
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In reply to this post by Marcus Denker-4
On 13 February 2018 at 17:25, Marcus Denker <[hidden email]> wrote:
This may remove a big reason for needing asClass, which was introduced so you could DoIt on a script to load a package and then operate on a class from that package before that class was defined.
I guess its partially a compiler issue. One way would be for the compiler to wrap the reference to SomeGlobal in an instance of UnknownGlobal. When a message is sent to that instance, it can check whether SomeGlobal is now defined (i.e. loaded earlier in the script) and forward the message to SomeGlobal.
yes. cheers -ben
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Re: canonical way to convert Symbol into Class (retrieve class by its name)
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The current Undeclared mechanism should make it easy: for every Undeclared, we do have a binding in Undeclared that binds the name to nil. Could be another value (some first class object). Maybe it could even put as the value the binging itself, which is already a subclass of Association called UndeclaredVariable. Marcus |
Re: canonical way to convert Symbol into Class (retrieve class by its name)
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Administrator
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In reply to this post by Marcus Denker-4
Marcus Denker-4 wrote
> Sometimes I think we should treat globals more in a “late bound” fashion. Late bound = power. I remember being very disappointed when I realized that classes are early bound by methods (resolved in literals). This makes things like class-side stubbing very difficult without jumping through hoops (e.g. process variables). ----- Cheers, Sean -- Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html
Cheers,
Sean |
Re: canonical way to convert Symbol into Class (retrieve class by its name)
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In reply to this post by Denis Kudriashov
Denis Kudriashov wrote: > > 2018-02-13 10:25 GMT+01:00 Marcus Denker <[hidden email] > <mailto:[hidden email]>>: > > Sometimes I think we should treat globals more in a “late bound” > fashion. > > e.g. right now we say that “Undeclared” vars are to be avoided at > any cost. > > But we could just treat them like we treat messages that are send > that do not exist. > > Forcing “#classNamed: “ for all unknown globals is a bit similar > than forcing to use “perform:” for > all unknown selectors. > > e.g. why have Smalltalk at: #SomeClass and react to it if you could > instead reason on the fact that > a variable is not bound (yet). > > SomeGlobal ifUndefined: [ ]. > > > I really like this idea. We just need to represent undefined variable > value as special object instead of nil. I don't like it for precisely this. In JS, there is undefined and null, and everyone hates that (despite maybe good intentions to split the two meanings). #SomeGlobal inContextOf: self ifUndefined: [ ... ] Maybe this could go if enough magic is done, though: [ SomeGlobal ] ifUndefined: [ ... ] > This way we would not obscure the fact that we are accessing a > global and we model explicitly the state > if it is bound or not. > > Would that no be better than hiding it behind an API to look up symbols? > > (just some thoughts, needs more thinking before action is possible) > > Marcus > >> On 11 Feb 2018, at 22:12, Richard Sargent >> <[hidden email] >> <mailto:[hidden email]>> wrote: >> >> There are two use cases that come immediately to mind. They may be >> the two most important. >> >> "As a Compiler, I need to be able to resolve a Symbol to a known >> Object." >> "As a Browser, I need to be able to identify the possible >> resolutions of a String to known Objects." >> >> >> I can elaborate on those, but I think they are pretty clear no >> matter what scopes, namespaces, environments, modules, or whatever >> one uses to organize things in the image. (One can even imagine an >> external registry of names that could be searched and yield up >> suggestions of external packages that would be needed.) >> >> On Sun, Feb 11, 2018 at 12:42 PM, Denis Kudriashov >> <[hidden email] <mailto:[hidden email]>> wrote: >> >> >> >> 2018-02-11 21:08 GMT+01:00 Stephane Ducasse >> <[hidden email] <mailto:[hidden email]>>: >> >> Denis >> >> we should introduce classNamed: now we can have traits and >> globals too :( >> >> >> Yes, we need to think about it. >> >> Idea? may be can still classNamed: >> >> Stef >> >> >> On Sun, Feb 11, 2018 at 8:55 PM, Denis Kudriashov >> <[hidden email] <mailto:[hidden email]>> wrote: >> > >> > >> > 2018-02-11 20:36 GMT+01:00 Hernán Morales Durand >> <[hidden email] <mailto:[hidden email]>>: >> >> >> >> 2018-02-11 16:10 GMT-03:00 Denis Kudriashov >> <[hidden email] <mailto:[hidden email]>>: >> >> > Hi Hernan. >> >> > >> >> > 2018-02-11 19:57 GMT+01:00 Hernán Morales Durand >> >> > <[hidden email] >> <mailto:[hidden email]>>: >> >> >> >> >> >> Hi Denis >> >> >> >> >> >> 2018-02-10 15:18 GMT-03:00 Denis Kudriashov >> <[hidden email] <mailto:[hidden email]>>: >> >> >> > >> >> >> > 2018-02-10 20:59 GMT+03:00 Stephane Ducasse >> >> >> > <[hidden email] >> <mailto:[hidden email]>>: >> >> >> >> >> >> >> >> Please to not use an unary on Symbol >> >> >> >> Dispatch on something. >> >> >> >> >> >> >> >> self class environment at: #Array >> >> >> >> is the best >> >> >> > >> >> >> > >> >> >> > We should not use collection API for reflection >> calls. It makes them >> >> >> > very >> >> >> > difficult to find. Let's use explicit names like: >> >> >> > >> >> >> >> >> >> Sorry I do not see it. >> >> >> >> >> >> The Collection API is beautiful, why couldn't be >> used for reflection? >> >> > >> >> > >> >> > We have around 3000 senders of #at: message in the >> image. Do you think >> >> > it is >> >> > easy to filter reflective calls? >> >> > >> >> >> >> I still don't understand your use case, nor how the >> #at: is related >> >> with the #asClass issue. >> >> >> >> Do you mean **further** filtering for relflective sends? >> >> >> >> Does this affects common-usage beyond Browser development? >> > >> > >> > The Stef proposal was that we should never use #asClass >> in the code. It is >> > fine for scripting but not for the domain code by many >> reasons which were >> > discussed here and at the past. >> > >> > But I only commented the proposed replacement: >> > >> > self class environment at: #Object >> > >> > >> > If you do not like it, it is different story. I just >> described problem with >> > #at: message: >> > >> > We already replaced many #asClass users with this code. >> And now it is quite >> > difficult to find such places. They all hidden inside >> 3000 senders of #at:. >> > If we will use #classNamed: instead of #at: then simple >> senders query will >> > easily detect all reflective calls. >> > (we probably already use it but not in all places). >> > >> >> >> >> >> >> >> >> >> >> I have no trouble finding #asClass senders, >> implementors, etc. >> >> >> >> >> >> What do you want to find? >> >> >> >> >> >> > self class environment classNamed: #Array >> >> >> > >> >> >> >> >> >> Too much typing :) >> >> >> >> >> >> > >> >> >> > From the other side we all agree that #asClass is >> super handy method. >> >> >> > And we >> >> >> > can fix it to respect sender environment using >> thisContext. It will >> >> >> > affects >> >> >> > performance but with our super powerful metalinks >> it can be easily >> >> >> > cached >> >> >> > (#asMethodConst is implemented that way). >> >> >> > So we can make environment completely transparent >> for users. >> >> >> > >> >> >> > Best regards, >> >> >> > Denis >> >> >> > >> >> >> >> >> >> >> >> For Modules, we made progress and got bitten by >> many issues and >> >> >> >> teaching >> >> >> >> load. >> >> >> >> >> >> >> >> >> >> >> >> Stef >> >> >> >> >> >> >> >> On Sat, Feb 10, 2018 at 4:50 PM, Clément Bera >> >> >> >> <[hidden email] >> <mailto:[hidden email]>> >> >> >> >> wrote: >> >> >> >> > On Sat, Feb 10, 2018 at 4:34 PM, Hernán Morales >> Durand >> >> >> >> > <[hidden email] >> <mailto:[hidden email]>> wrote: >> >> >> >> >> >> >> >> >> >> Hi Clément, >> >> >> >> >> >> >> >> >> >> First time I read about modules in Pharo. >> >> >> >> >> What is a module exactly? >> >> >> >> >> >> >> >> >> >> What's the problem to solve? >> >> >> >> > >> >> >> >> > >> >> >> >> > It's similar to namespaces with some different, >> arguably better, >> >> >> >> > features. >> >> >> >> > >> >> >> >> > Honestly I am not the expert on it so I would >> like some one else >> >> >> >> > to >> >> >> >> > answer. >> >> >> >> > >> >> >> >> > Among other things, it solves the problem of >> having 2 classes with >> >> >> >> > the >> >> >> >> > same >> >> >> >> > name (avoiding the prefixes we have like in C). >> But reportedly >> >> >> >> > that's >> >> >> >> > just a >> >> >> >> > side-effect and not the main problem to solve. >> >> >> >> > >> >> >> >> >> >> >> >> >> >> Cheers, >> >> >> >> >> >> >> >> >> >> Hernán >> >> >> >> >> >> >> >> >> >> 2018-02-10 9:47 GMT-03:00 Clément Bera >> <[hidden email] <mailto:[hidden email]>>: >> >> >> >> >> > Hi, >> >> >> >> >> > >> >> >> >> >> > In short, everything that is not >> namespace/module compatible >> >> >> >> >> > will >> >> >> >> >> > be >> >> >> >> >> > deprecated/changed/removed in the future, so >> it is not >> >> >> >> >> > recommended >> >> >> >> >> > to >> >> >> >> >> > use >> >> >> >> >> > it. >> >> >> >> >> > >> >> >> >> >> > a.2) #Array asClassInEnvironment: Smalltalk >> globals >> >> >> >> >> > b.1) Smalltalk globals at: #Array >> >> >> >> >> > => Ok-ish, note that you may need to change >> 'Smalltalk globals' >> >> >> >> >> > the >> >> >> >> >> > namespace/module when support for those will >> be added since >> >> >> >> >> > Array >> >> >> >> >> > will >> >> >> >> >> > be in >> >> >> >> >> > a module. >> >> >> >> >> > Maybe you want instead to use instead: >> >> >> >> >> > >> >> >> >> >> > c) self class environment at: #Array >> >> >> >> >> > => this will work in the future if your code >> is a class which >> >> >> >> >> > environment/namespace/module includes the >> Array class you would >> >> >> >> >> > expect >> >> >> >> >> > >> >> >> >> >> > a.1) #Array asClass >> >> >> >> >> > b.2) Smalltalk at: #Array >> >> >> >> >> > b.3) Smalltalk classNamed: #Array >> >> >> >> >> > => In which namespace/module are you looking >> for #Array ? In >> >> >> >> >> > the >> >> >> >> >> > future >> >> >> >> >> > this >> >> >> >> >> > may be removed, alternatively it will work >> only for globals but >> >> >> >> >> > not >> >> >> >> >> > globals >> >> >> >> >> > inside namespace/module which won't work >> since Array will be in >> >> >> >> >> > a >> >> >> >> >> > module. >> >> >> >> >> > >> >> >> >> >> > >> >> >> >> >> > On Sat, Feb 10, 2018 at 12:57 PM, Peter Uhnák >> >> >> >> >> > <[hidden email] <mailto:[hidden email]>> >> >> >> >> >> > wrote: >> >> >> >> >> >> >> >> >> >> >> >> Hi, >> >> >> >> >> >> >> >> >> >> >> >> what is the canonical way to get a class >> from a symbol? >> >> >> >> >> >> >> >> >> >> >> >> a) Converting symbol into class via string >> protocol >> >> >> >> >> >> >> >> >> >> >> >> a.1) #Array asClass >> >> >> >> >> >> I use this the most, because it is easy, >> uses unary selector, >> >> >> >> >> >> and >> >> >> >> >> >> so >> >> >> >> >> >> far >> >> >> >> >> >> I've never ran into any issues. But >> apparently it is not good >> >> >> >> >> >> -- >> >> >> >> >> >> why? >> >> >> >> >> >> >> >> >> >> >> >> a.2) #Array asClassInEnvironment: Smalltalk >> globals >> >> >> >> >> >> >> >> >> >> >> >> b) Retriving the class by key from the >> system dictionary >> >> >> >> >> >> >> >> >> >> >> >> b.1) Smalltalk globals at: #Array >> >> >> >> >> >> >> >> >> >> >> >> b.2) Smalltalk at: #Array >> >> >> >> >> >> >> >> >> >> >> >> b.3) Smalltalk classNamed: #Array >> >> >> >> >> >> >> >> >> >> >> >> c) something else entirely? >> >> >> >> >> >> >> >> >> >> >> >> I get that using #asClass wouldn't work if >> there was a >> >> >> >> >> >> different >> >> >> >> >> >> environment, however I don't even know in >> what situation there >> >> >> >> >> >> could >> >> >> >> >> >> be >> >> >> >> >> >> a >> >> >> >> >> >> different environment, so I cannot assert >> how problematic it >> >> >> >> >> >> is >> >> >> >> >> >> or >> >> >> >> >> >> isn't. >> >> >> >> >> >> >> >> >> >> >> >> Thanks, >> >> >> >> >> >> Peter >> >> >> >> >> > >> >> >> >> >> > >> >> >> >> >> > >> >> >> >> >> > >> >> >> >> >> > -- >> >> >> >> >> > Clément Béra >> >> >> >> >> > Pharo consortium engineer >> >> >> >> >> > https://clementbera.wordpress.com/ >> <https://clementbera.wordpress.com/> >> >> >> >> >> > Bâtiment B 40, avenue Halley 59650 >> Villeneuve d >> <https://maps.google.com/?q=40,+avenue+Halley+59650+Villeneuve+d%27Ascq&entry=gmail&source=g>' >> <https://maps.google.com/?q=40,+avenue+Halley+59650+Villeneuve+d'Ascq+%3Chttps://maps.google.com/?q%3D40,%2Bavenue%2BHalley%2B59650%2BVilleneuve%2Bd%2527Ascq%26entry%3Dgmail%26source%3Dg%3E&entry=gmail&source=g>Ascq >> <https://maps.google.com/?q=40,+avenue+Halley+59650+Villeneuve+d%27Ascq&entry=gmail&source=g> >> >> >> >> >> >> >> >> >> > >> >> >> >> > >> >> >> >> > >> >> >> >> > -- >> >> >> >> > Clément Béra >> >> >> >> > Pharo consortium engineer >> >> >> >> > https://clementbera.wordpress.com/ >> <https://clementbera.wordpress.com/> >> >> >> >> > Bâtiment B 40, avenue Halley 59650 Villeneuve d >> <https://maps.google.com/?q=40,+avenue+Halley+59650+Villeneuve+d%27Ascq&entry=gmail&source=g>' >> <https://maps.google.com/?q=40,+avenue+Halley+59650+Villeneuve+d'Ascq+%3Chttps://maps.google.com/?q%3D40,%2Bavenue%2BHalley%2B59650%2BVilleneuve%2Bd%2527Ascq%26entry%3Dgmail%26source%3Dg%3E&entry=gmail&source=g>Ascq >> <https://maps.google.com/?q=40,+avenue+Halley+59650+Villeneuve+d%27Ascq&entry=gmail&source=g> >> >> >> >> >> >> >> > >> >> >> >> >> > >> >> >> > >> >> >> > > |
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