- Pharo-users - lists.pharo.org

Re: [Pharo-users] Modeling HABTM

by Esteban Maringolo

By reference I mean an instance variable. So it's the same thing. But it's not that one object has two "parents" (this isn't a tree like structure). The object (it is, the Track) has two references to the Episodes where it appears, such reference happens because aTrack as a instance variable "holding" (aka "referencing") aCollection, and this collection "contains" (it is, references) two elements, that are the Episodes in which a track appears. For the sake of simplicity, you should define who must perform the "maintenance" of the collections on only one sides. In my opinion it should be the Episode. E.g. Episode>>addTrackToPlaylist: aTrack self playlist add: aTrack. aTrack includeInEpisode: self Episode>>playlist playlist ifNil: [playlist := OrderedCollection new]. Track>>includeInEpisode: anEpisode self episodes add: anEpisode Track>>#episodes episodes ifNil: [episodes := Set new] You can see that #includeInEpisode: doesn't add itself to the Episode, because it is very likely that the interaction is started onto the Episode and not the Track. Otherwise to avoid a recursion you should have a condition like: Episode>>addTrackToPlaylist: aTrack (self playlist includes: aTrack) ifFalse: [ self playlist add: aTrack. aTrack includeInEpisode: self ] Track>>includeInEpisode: anEpisode self episodes add: anEpisode. anEpisode addTrackToPlaylist: self The paper about "Mutual Friends" talks about the pro's and cons of different approaches. Esteban A. Maringolo On Mon, Jun 10, 2019 at 2:40 PM sergio ruiz <sergio.rrd(a)gmail.com> wrote: > > when you say references, how does this look in pharo? I donât know that I have used such a relationship. > > I was thinking that an object would have an instance variable that was an ordered collection of objects.. So having one object belong to two parent objects could be tricky. > > > > On Jun 10, 2019, at 1:27 PM, Esteban Maringolo <emaringolo(a)gmail.com> wrote: > > You have anEpisode that references a collection with instances of Track. > And each Track has a collection of episodes. > > > ---- > peace, > sergio > photographer, journalist, visionary > > Public Key: http://bit.ly/29z9fG0 > #BitMessage BM-NBaswViL21xqgg9STRJjaJaUoyiNe2dV > http://www.codeandmusic.com > http://www.twitter.com/sergio_101 > http://www.facebook.com/sergio101 >

June 10, 2019

Re: [Pharo-users] Modeling HABTM

by sergio ruiz

when you say references, how does this look in pharo? I donât know that I have used such a relationship. I was thinking that an object would have an instance variable that was an ordered collection of objects.. So having one object belong to two parent objects could be tricky. > On Jun 10, 2019, at 1:27 PM, Esteban Maringolo <emaringolo(a)gmail.com> wrote: > > You have anEpisode that references a collection with instances of Track. > And each Track has a collection of episodes. ---- peace, sergio photographer, journalist, visionary Public Key: http://bit.ly/29z9fG0 #BitMessage BM-NBaswViL21xqgg9STRJjaJaUoyiNe2dV http://www.codeandmusic.com http://www.twitter.com/sergio_101 http://www.facebook.com/sergio101

June 10, 2019

Re: [Pharo-users] Modeling HABTM

by James Foster

Sergio, When you have a two-way relationship, one option is to keep duplicate information and use it to go from one object to the others. The advantage is rapid lookup, but the disadvantage is the need to update multiple places to maintain consistency (as well as the space it takes). Another option is to keep the relationship in only one place and then do a search for the secondary relationship on each lookup. So, each episode has a collection of tracks and the episode to tracks lookup is direct. If you have a track and want to find the episodes, then you query each episode to see if it includes that track. The advantage is simplicity of design and maintenance (the internal structures are never inconsistent; wrong, maybe, but never inconsistent!). The disadvantage is extra time doing the lookup. But before you discount this approach, ask yourself what performance penalty this will cost. How many episodes? How many tracks? Do you have less than 10K of each? How many milliseconds does it take to do a âbrute-forceâ search? I strongly recommend: * Make it work, [and only then] * Make it right, [and only then, if really needed] * Make it fast Do the simplest thing that can possibly work, and that is to have one one set of references. Donât add complexity till you need it. Hide (encapsulate) the implementation so you can change it later if needed. Another approach is to use a tool that provides automatic references. GemStone includes indexes that are managed by the system, so you can just ask the index for all episodes that reference a track. You only update one data structure but the system manages more. James > On Jun 10, 2019, at 5:20 AM, sergio ruiz <sergio.rrd(a)gmail.com> wrote: > > I am currently putting together a Seaside website for my radio show. I am trying to figure out how to model the "has and belongs to many" relationships. > > Each episode can have many tracks, each of these tracks can belong to several episodes. > I want to be able to present a listing of which episodes each track appears in, and a listing of tracks for each episode. > > The approach I have seen on this is to create an intermediary object and store a set of ids on this, but this seems a little clunky, and it seems like there would be a clean way to do this. > Am I missing something? > Thanks! > > > ---- > peace, > sergio > photographer, journalist, visionary > > Public Key: http://bit.ly/29z9fG0 <http://bit.ly/29z9fG0> > #BitMessage BM-NBaswViL21xqgg9STRJjaJaUoyiNe2dV > http://www.codeandmusic.com <http://www.codeandmusic.com/> > http://www.twitter.com/sergio_101 > http://www.facebook.com/sergio101 >

June 10, 2019

Dr. Geo release 19.06a

by Hilaire

I am please to announce the Dr. Geo release 19.06, the GNU interactive geometry software. It follows the release 19.03 in March 2019. - New features - Bugs fix - Updated French user guide <http://drgeo.eu/help> - New book "Programmer des math avec Dr. Geo" <http://drgeo.eu/help>. WIP - Feedback appreciated! See details in the change log file in the software or read the bugs fix list <https://launchpad.net/drgeo/trunk/19.06>. Download <http://drgeo.eu/download>. Hilaire -- Dr. Geo http://drgeo.eu

June 10, 2019

Re: [Pharo-users] Modeling HABTM

by Esteban Maringolo

The M:N relationship is pretty straightforward in pure OO design. You have anEpisode that references a collection with instances of Track. And each Track has a collection of episodes. Of course this could be elaborated even further, and have an object like TrackPlay sitting in between of anEpisode and aTrack. This TrackPlay object could have extra information, like the timespan at which it was played, the date (although this could be delegated to the Episode itself). It doesn't happen much these days, but a billboard hit was played more than once, so with a TrackPlay you could log both plays and know when each one was played. So Episode "has many" TrackPlay TrackPlay "references" Episode and Track The Track could "has many" Episodes (and ask them for the TrackPlays of itself) or "has many" references TrackPlay. And you can make things even more elaborated, but I'd go for the "TrackPlay" (for the lack of a better name) path. Regards, Esteban A. Maringolo On Mon, Jun 10, 2019 at 9:21 AM sergio ruiz <sergio.rrd(a)gmail.com> wrote: > > I am currently putting together a Seaside website for my radio show. I am trying to figure out how to model the "has and belongs to many" relationships. > > Each episode can have many tracks, each of these tracks can belong to several episodes. > I want to be able to present a listing of which episodes each track appears in, and a listing of tracks for each episode. > > The approach I have seen on this is to create an intermediary object and store a set of ids on this, but this seems a little clunky, and it seems like there would be a clean way to do this. > Am I missing something? > Thanks! > > > ---- > peace, > sergio > photographer, journalist, visionary > > Public Key: http://bit.ly/29z9fG0 > #BitMessage BM-NBaswViL21xqgg9STRJjaJaUoyiNe2dV > http://www.codeandmusic.com > http://www.twitter.com/sergio_101 > http://www.facebook.com/sergio101 >

June 10, 2019

Re: [Pharo-users] Modeling HABTM

by sergio ruiz

Thanks! Iâll look at this. Iâd like to keep it in the OO domain.. There is no existing data. Everything would be created for this project. > On Jun 10, 2019, at 12:53 PM, Ben Coman <btc(a)openinworld.com> wrote: > > If you are keeping your design purely in the object-oriented domain, > you might try Mutual Friends... https://pdfs.semanticscholar.org/348f/e4ecff3c23f3709bb88e7e60379905a3b930.… <https://pdfs.semanticscholar.org/348f/e4ecff3c23f3709bb88e7e60379905a3b930.…> > although I've not enough experience with it to know if its the best way. > ---- peace, sergio photographer, journalist, visionary Public Key: http://bit.ly/29z9fG0 #BitMessage BM-NBaswViL21xqgg9STRJjaJaUoyiNe2dV http://www.codeandmusic.com http://www.twitter.com/sergio_101 http://www.facebook.com/sergio101

June 10, 2019

Re: [Pharo-users] Modeling HABTM

by Ben Coman

On Mon, 10 Jun 2019 at 20:21, sergio ruiz <sergio.rrd(a)gmail.com> wrote: > I am currently putting together a Seaside website for my radio show. I am > trying to figure out how to model the "has and belongs to many" > relationships. > > Each episode can have many tracks, each of these tracks can belong to > several episodes. > I want to be able to present a listing of which episodes each track > appears in, and a listing of tracks for each episode. > > The approach I have seen on this is to create an intermediary object and > store a set of ids on this, but this seems a little clunky, and it seems > like there would be a clean way to do this. > This is how you'd model many-to-many relationships in relational databases. https://dzone.com/articles/how-to-handle-a-many-to-many-relationship-in-dat… If that is where your data is stored, you may be forced to this. If you are keeping your design purely in the object-oriented domain, you might try Mutual Friends... https://pdfs.semanticscholar.org/348f/e4ecff3c23f3709bb88e7e60379905a3b930.… although I've not enough experience with it to know if its the best way. Or you might try relation slots. Check out SlotExampleMovieAndPersonTest. Some background reading... https://rmod.inria.fr/archives/papers/Verw11a-OOSPLA11-FlexibleObjectLayout… which I'd guess is still useful even if I read somewhere it was a bit out of date. cheers -ben

June 10, 2019

Modeling HABTM

by sergio ruiz

I am currently putting together a Seaside website for my radio show. I am trying to figure out how to model the "has and belongs to many" relationships. Each episode can have many tracks, each of these tracks can belong to several episodes. I want to be able to present a listing of which episodes each track appears in, and a listing of tracks for each episode. The approach I have seen on this is to create an intermediary object and store a set of ids on this, but this seems a little clunky, and it seems like there would be a clean way to do this. Am I missing something? Thanks! ---- peace, sergio photographer, journalist, visionary Public Key: http://bit.ly/29z9fG0 #BitMessage BM-NBaswViL21xqgg9STRJjaJaUoyiNe2dV http://www.codeandmusic.com http://www.twitter.com/sergio_101 http://www.facebook.com/sergio101

June 10, 2019

Re: [Pharo-users] IceGenericError: Failed to connect to github.com: Interrupted system call

by HernÃ¡n Morales Durand

Attached the Stack in FUEL format in case someone want to check it out Cheers, HernÃ¡n El dom., 9 jun. 2019 a las 20:25, HernÃ¡n Morales Durand (< hernan.morales(a)gmail.com>) escribiÃ³: > Hi guys, > > > In Pharo 7.0.3 I get an Iceberg error while cloning a repository. I tried > to fix dependent repositories, I guess there is something weird in > Diacriticals (https://github.com/hernanmd/Diacriticals) however I have no > clue what's wrong there. > > > I can reproduce it in a clean image by evaluating: > > > Metacello new > > baseline: 'StringExtensions'; > > repository: 'github://hernanmd/StringExtensions/repository'; > > load. > > > Any idea what could be wrong? > > > Cheers, > > > HernÃ¡n > > >

June 10, 2019

IceGenericError: Failed to connect to github.com: Interrupted system call

by HernÃ¡n Morales Durand

Hi guys, In Pharo 7.0.3 I get an Iceberg error while cloning a repository. I tried to fix dependent repositories, I guess there is something weird in Diacriticals (https://github.com/hernanmd/Diacriticals) however I have no clue what's wrong there. I can reproduce it in a clean image by evaluating: Metacello new baseline: 'StringExtensions'; repository: 'github://hernanmd/StringExtensions/repository'; load. Any idea what could be wrong? Cheers, HernÃ¡n

June 9, 2019