# About class methods **URL:** \ **Category:** ruby-talk\ **Created:** [8 December 2005 06:30 UTC](https://rubytalk.org/t/about-class-methods/23105 "2005-12-08T06:30:00Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Hank\_Gong](https://avatars.discourse-cdn.com/v4/letter/h/ac91a4/32.png) [@Hank\_Gong](https://rubytalk.org/u/Hank_Gong)\ **Post date:** [8 December 2005 06:30 UTC](https://rubytalk.org/t/about-class-methods/23105/1 "2005-12-08T06:30:00Z")
Hi! When I read the Ruby manual, I noticed that for class Array, there are class methods and instance methods. Class methods: [] and new instance methods: too many (not list here) My question is: what's this class methods? I remember in C++, all methods should be instance level, right? Thanks! Yours, Hank ---
**Author:** ![Logan\_Capaldo](https://avatars.discourse-cdn.com/v4/letter/l/7ea924/32.png) [@Logan\_Capaldo](https://rubytalk.org/u/Logan_Capaldo)\ **Post date:** [8 December 2005 06:39 UTC](https://rubytalk.org/t/about-class-methods/23105/2 "2005-12-08T06:39:27Z")
> Hi! When I read the Ruby manual, I noticed that for class Array, there are > class methods and instance methods. > > Class methods: > and new > > instance methods: > too many (not list here) > > My question is: what's this class methods? I remember in C++, all methods > should be instance level, right? > Thanks! > > Yours, Hank class methods are (more or less) the same thing as static methods in C++. eg. class A {     public:      static int aClassMethod { return 42; }      int anInstanceMethod { return 7; } }; A x; x.anInstanceMethod( ); //=\> returns 7 > **路路路** > > On Dec 8, 2005, at 1:30 AM, Hank Gong wrote: > A::aClassMethod( ); //=\> returns 42 ---
**Author:** ![James\_Britt4](https://avatars.discourse-cdn.com/v4/letter/j/a3d4f5/32.png) [@James\_Britt4](https://rubytalk.org/u/James_Britt4)\ **Post date:** [8 December 2005 06:52 UTC](https://rubytalk.org/t/about-class-methods/23105/3 "2005-12-08T06:52:19Z")
Hank Gong wrote: > Hi! When I read the Ruby manual, I noticed that for class Array, there are > class methods and instance methods. > > Class methods: > and new > > instance methods: > too many (not list here) > > My question is: what's this class methods? I remember in C++, all methods > should be instance level, right? p Array.class # Class p Array.instance\_of? Class # true Array is an instance of Class, so those methods are, in a way, instance methods. No? They're not eigenmethods are they? 馃檪 James > **路路路** > > -- > > [http://www.ruby-doc.org](http://www.ruby-doc.org) - Ruby Help & Documentation > [Ruby Code & Style](http://www.artima.com/rubycs/) - Ruby Code & Style: Writers wanted > [http://www.rubystuff.com](http://www.rubystuff.com) - The Ruby Store for Ruby Stuff > [http://www.jamesbritt.com](http://www.jamesbritt.com) - Playing with Better Toys > [http://www.30secondrule.com](http://www.30secondrule.com) - Building Better Tools ---
**Author:** ![7rans](https://avatars.discourse-cdn.com/v4/letter/7/a8b319/32.png) [@7rans](https://rubytalk.org/u/7rans)\ **Post date:** [8 December 2005 06:57 UTC](https://rubytalk.org/t/about-class-methods/23105/4 "2005-12-08T06:57:35Z")
In Ruby a class is an object too. So it can have it's own methods just like any other object. There methods are different from a class instance methods, which are the ones that define the nature of an object instantiated from the class. So lets say we have a class:   class MyClass   end Then we can treat is like any other object and send messages to it.   MyClass.object\_id #=\> -606921464 That's what is called a \*class method\*. Also, you may have noticed that you can define a method tailored specifically for any object. For instance:   a = "hi"   def a.up     self.upcase   end   a.up #=\> "HI" Class methods are actually the same thing. You can create one of these tailor-made methods for a class likewise:   def MyClass.upname     name.upcase   end   MyClass.upname #=\> "MYCLASS" HTH, T. (Hey all, I didn't use the term adhoc! See I can take a hin... I mean a brick to the head 馃槈 ---
**Author:** ![7rans](https://avatars.discourse-cdn.com/v4/letter/7/a8b319/32.png) [@7rans](https://rubytalk.org/u/7rans)\ **Post date:** [8 December 2005 07:02 UTC](https://rubytalk.org/t/about-class-methods/23105/5 "2005-12-08T07:02:39Z")
> They're not eigenmethods are they? > > 馃檪 Actually, they are ad hoc. 馃槈 ---
**Author:** ![7rans](https://avatars.discourse-cdn.com/v4/letter/7/a8b319/32.png) [@7rans](https://rubytalk.org/u/7rans)\ **Post date:** [8 December 2005 14:32 UTC](https://rubytalk.org/t/about-class-methods/23105/6 "2005-12-08T14:32:45Z")
Sorry Hank, if you are unware of what were talking about in these last two posts. We're refering to a very recent thread that discussed what to call these type of methods. Presently they are known a "singleton methods", but becuase of the clash with what is known in OOP generally as the \*singleton pattern\*, there is on-going discussion on finding a better term. Recent alternative suggestions are "eigen" and "adhoc". T. ---
**Author:** ![Hank\_Gong](https://avatars.discourse-cdn.com/v4/letter/h/ac91a4/32.png) [@Hank\_Gong](https://rubytalk.org/u/Hank_Gong)\ **Post date:** [8 December 2005 18:30 UTC](https://rubytalk.org/t/about-class-methods/23105/7 "2005-12-08T18:30:16Z")
I carefully read two articles about classmethods and singleton concept. Now for me, the concept of classmethods seems not difficult for me now. It's just singleton methods for a class because class is also a object. However, the concept of singleton still not clear for me, also how to use them is also not making sense for me. Yours, Hank > **路路路** > > On 12/8/05, Trans \ wrote: > > > Sorry Hank, if you are unware of what were talking about in these last > > two posts. We're refering to a very recent thread that discussed what > > to call these type of methods. Presently they are known a "singleton > > methods", but becuase of the clash with what is known in OOP generally > > as the \*singleton pattern\*, there is on-going discussion on finding a > > better term. Recent alternative suggestions are "eigen" and "adhoc". > > > > T. ---
**Author:** ![Mark4](https://avatars.discourse-cdn.com/v4/letter/m/77aa72/32.png) [@Mark4](https://rubytalk.org/u/Mark4)\ **Post date:** [12 December 2005 06:02 UTC](https://rubytalk.org/t/about-class-methods/23105/8 "2005-12-12T06:02:29Z")
I'm curious why "class method" is being avoided? It certainly seems accurate and matches the use of class methods by languages such as Smalltalk and Objective-C. > **路路路** > > On 12/8/05, Trans \ wrote: > > > Sorry Hank, if you are unware of what were talking about in these last > > two posts. We're refering to a very recent thread that discussed what > > to call these type of methods. Presently they are known a "singleton > > methods", but becuase of the clash with what is known in OOP generally > > as the \*singleton pattern\*, there is on-going discussion on finding a > > better term. Recent alternative suggestions are "eigen" and "adhoc". > > > > T. ---
**Author:** ![David\_A\_Black3](https://avatars.discourse-cdn.com/v4/letter/d/6a8cbe/32.png) [@David\_A\_Black3](https://rubytalk.org/u/David_A_Black3)\ **Post date:** [8 December 2005 19:00 UTC](https://rubytalk.org/t/about-class-methods/23105/9 "2005-12-08T19:00:54Z")
Hi -- > I carefully read two articles about classmethods and singleton concept. > Now for me, the concept of classmethods seems not difficult for me now. It's > just singleton methods for a class because class is also a object. > However, the concept of singleton still not clear for me, also how to use > them is also not making sense for me. Basically an object's singleton class is a class created ad hoc, and in a sense retroactively, for the sole purpose of being the-class-where-this-object's-singleton-methods are defined and live. David P.S. Aside to Tom S.: I agree it's ad hoc in the sense of being for a specific purpose, but I'm not sure I agree that it's ad hoc where the "hoc" (actually the "hic", I guess, in the nominative case 馃檪 is the object itself. One then runs into questions like: are instance variables "ad hoc" variables? etc. > **路路路** > > On Fri, 9 Dec 2005, Hank Gong wrote: > > -- > David A. Black > dblack@wobblini.net > > "Ruby for Rails", forthcoming from Manning Publications, April 2006! ---
**Author:** ![HAL\_9000](https://avatars.discourse-cdn.com/v4/letter/h/90ced4/32.png) [@HAL\_9000](https://rubytalk.org/u/HAL_9000)\ **Post date:** [12 December 2005 06:30 UTC](https://rubytalk.org/t/about-class-methods/23105/10 "2005-12-12T06:30:50Z")
Mark Ericson wrote: > I'm curious why "class method" is being avoided? It certainly seems > accurate and matches the use of class methods by languages such as Smalltalk > and Objective-C. I think "class method" is used in our community, but it is considered a special case -- it's just a singleton method on an object which happens to be a class. A singleton method on an object which isn't a class -- well, that obviously isn't a class method. Hal ---
**Author:** ![7rans](https://avatars.discourse-cdn.com/v4/letter/7/a8b319/32.png) [@7rans](https://rubytalk.org/u/7rans)\ **Post date:** [8 December 2005 20:03 UTC](https://rubytalk.org/t/about-class-methods/23105/11 "2005-12-08T20:03:49Z")
dblack@wobblini.net wrote: > P.S. Aside to Tom S.: I agree it's ad hoc in the sense of being for a > specific purpose, but I'm not sure I agree that it's ad hoc where the > "hoc" (actually the "hic", I guess, in the nominative case 馃檪 is the > object itself. One then runs into questions like: are instance > variables "ad hoc" variables? etc. Interesting. Perhaps we've met halfway then. 'Ad hoc' is an excellent discriptive term, but in trying it on for size some more, so to speak, I'm not as certain that it makes a good \*techncal\* term, not because of negative conotations, but because it may be too generic, much like 'meta'. Which I think it is what you're pointing out here. Of course, this might be a problem with any term that doesn't already have a fitting techincal meaning. T. ---
**Author:** ![Sean\_O\_Halpin](https://avatars.discourse-cdn.com/v4/letter/s/ac91a4/32.png) [@Sean\_O\_Halpin](https://rubytalk.org/u/Sean_O_Halpin)\ **Post date:** [8 December 2005 22:54 UTC](https://rubytalk.org/t/about-class-methods/23105/12 "2005-12-08T22:54:24Z")
Heu magister carbunculi! 馃槈 Ridens magna voce Iohannes > **路路路** > > On 12/8/05, dblack@wobblini.net \ wrote: > > > I'm not sure I agree that it's ad hoc where the > > "hoc" (actually the "hic", I guess, in the nominative case 馃檪 is the > > object itself. ---
**Author:** ![Chad\_Perrin1](https://avatars.discourse-cdn.com/v4/letter/c/977dab/32.png) [@Chad\_Perrin1](https://rubytalk.org/u/Chad_Perrin1)\ **Post date:** [12 December 2005 08:07 UTC](https://rubytalk.org/t/about-class-methods/23105/13 "2005-12-12T08:07:34Z")
By the way . . . has anyone considered a name like "singular"? What about "ad lib" instead of "ad hoc"? I've gotta say, though, that I'm partial to the descriptor "eigen". > **路路路** > > On Mon, Dec 12, 2005 at 03:30:50PM +0900, Hal Fulton wrote: > > > Mark Ericson wrote: > > \>I'm curious why "class method" is being avoided? It certainly seems > > \>accurate and matches the use of class methods by languages such as > > \>Smalltalk > > \>and Objective-C. > > > > I think "class method" is used in our community, but it is considered > > a special case -- it's just a singleton method on an object which happens > > to be a class. A singleton method on an object which isn't a class -- > > well, that obviously isn't a class method. > > -- > Chad Perrin [CCD CopyWrite | [http://ccd.apotheon.org](http://ccd.apotheon.org) ] > > unix virus: If you're using a unixlike OS, please forward > this to 20 others and erase your system partition. ---
**Author:** ![Jonathan\_zjll9](https://avatars.discourse-cdn.com/v4/letter/j/858c86/32.png) [@Jonathan\_zjll9](https://rubytalk.org/u/Jonathan_zjll9)\ **Post date:** [8 December 2005 20:45 UTC](https://rubytalk.org/t/about-class-methods/23105/14 "2005-12-08T20:45:05Z")
transfire wrote: > > P.S. Aside to Tom S.: I agree it's ad hoc in the sense of being for a > > specific purpose, but I'm not sure I agree that it's ad hoc where the > > "hoc" (actually the "hic", I guess, in the nominative case 馃檪 is the > > object itself. One then runs into questions like: are instance > > variables "ad hoc" variables? etc. > > Interesting. Perhaps we've met halfway then. 'Ad hoc' is an excellent > discriptive term, but in trying it on for size some more, so to speak, > I'm not as certain that it makes a good \*techncal\* term, not because of > negative conotations, but because it may be too generic, much like > 'meta'. Which I think it is what you're pointing out here. Of course, > this might be a problem with any term that doesn't already have a > fitting techincal meaning. > > T. What did you guys think about using simpleton to refer to these methods/classes? That way there can be differentiation between a class which was made single by 'include singleton' (that is, has one single instance somewhere) and a class which is made single (or simple) by having only class methods and class data. The one which is an instance of the design pattern could be called 'singleton' (since it isn't the one in question anyway) and the other could be called 'simpleton'. --J > **路路路** > > > dblack@wobblini.net wrote: > > -- > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C). ---
**Author:** ![Anonymous\_Coward](https://avatars.discourse-cdn.com/v4/letter/a/94ad74/32.png) [@Anonymous\_Coward](https://rubytalk.org/u/Anonymous_Coward)\ **Post date:** [12 December 2005 08:37 UTC](https://rubytalk.org/t/about-class-methods/23105/15 "2005-12-12T08:37:30Z")
I advocate "pouch" 馃檪 In any case, it might be wise to hold some sort of a poll (or perhaps Matz can be coerced to pick the one he prefers) because I have noticed a trend of different groups using different terms for the same thing which in turn has caused some confusion about the feature in general. E > **路路路** > > On 2005.12.12 17:07, Chad Perrin \ wrote: > > > On Mon, Dec 12, 2005 at 03:30:50PM +0900, Hal Fulton wrote: > > \> Mark Ericson wrote: > > \> \>I'm curious why "class method" is being avoided? It certainly seems > > \> \>accurate and matches the use of class methods by languages such as > > \> \>Smalltalk > > \> \>and Objective-C. > > \> > > \> I think "class method" is used in our community, but it is considered > > \> a special case -- it's just a singleton method on an object which happens > > \> to be a class. A singleton method on an object which isn't a class -- > > \> well, that obviously isn't a class method. > > > > By the way . . . has anyone considered a name like "singular"? What > > about "ad lib" instead of "ad hoc"? > > > > I've gotta say, though, that I'm partial to the descriptor "eigen". ---
**Author:** ![Dave\_Howell2](https://avatars.discourse-cdn.com/v4/letter/d/7ab992/32.png) [@Dave\_Howell2](https://rubytalk.org/u/Dave_Howell2)\ **Post date:** [13 December 2005 09:35 UTC](https://rubytalk.org/t/about-class-methods/23105/16 "2005-12-13T09:35:40Z")
Well, I'm having a terrible time following the distinction between the indefinite number of flavors of this difficult-to-name type of method, but I do know something about naming things. 馃檪 Generally, trying to find an existing term, like 'singleton' or 'ad hoc', is a good thing, because lets somebody bring pre-constructed expectations to the process, hopefully saving them time in learning how this particular thing works. Unless, of course, different people have different expectations for that word, or if the thing in question contradicts the expectations in some way. If 'simpleton' and 'singleton' are equally applicable to either of two different cases, as somebody suggested earlier, then these will lead people to \*think\* they know what will happen, but there's a 50/50 chance that it will be the other. So that's not a good thing. There appears to be some concern that "ad hoc" implies something much broader (?) than this particular usage actually has. That's not a good thing. If you have a situation where none of the existing reasonable terms seem like an adequately non-confusing match, then it's actually much better to use a term that \*doesn't\* bring a lot of pre-conceived baggage to the table. If you create a term that's \*obviously\* meaningless or ambiguous, then the first-time user knows right away that they'll have to look it up, instead of erroneously thinking they know what it does just because of the name. Calling them something like "intral methods", "uni methods", "anonic methods," or "eigenz" is better than using a "real" pre-existing word that is a poor fit. "Hmm. Uni methods. Well, I have a hunch what that might be for, but it isn't immediately obvious. I'll just have to read more about it to find out what they actually do." > **路路路** > > On Dec 12, 2005, at 0:07, Chad Perrin wrote: > > > By the way . . . has anyone considered a name like "singular"? What > > about "ad lib" instead of "ad hoc"? > > > > I've gotta say, though, that I'm partial to the descriptor "eigen". ---
**Author:** ![Gary\_Wright](https://avatars.discourse-cdn.com/v4/letter/g/58956e/32.png) [@Gary\_Wright](https://rubytalk.org/u/Gary_Wright)\ **Post date:** [8 December 2005 21:59 UTC](https://rubytalk.org/t/about-class-methods/23105/17 "2005-12-08T21:59:44Z")
> What did you guys think about using simpleton to refer to these > methods/classes? I'd vote no on that name regardless. If you think 'ad hoc' has negative connotations... >   That way there can be differentiation between a class > which was made single by 'include singleton' (that is, has one single > instance somewhere) and a class which is made single (or simple) by > having only class methods and class data. Are you confusing a class that has no instances (yet) with the class returned by the expression (class \<\ **路路路** > > On Dec 8, 2005, at 3:45 PM, jonathan \ \ \ wrote: ---
**Author:** ![Michael\_Ulm](https://avatars.discourse-cdn.com/v4/letter/m/a9adbd/32.png) [@Michael\_Ulm](https://rubytalk.org/u/Michael_Ulm)\ **Post date:** [13 December 2005 10:02 UTC](https://rubytalk.org/t/about-class-methods/23105/18 "2005-12-13T10:02:18Z")
Dave Howell wrote: > > By the way . . . has anyone considered a name like "singular"? What > > about "ad lib" instead of "ad hoc"? > > > > I've gotta say, though, that I'm partial to the descriptor "eigen". --snip-- > If you have a situation where none of the existing reasonable terms seem like an adequately non-confusing match, then it's actually much better to use a term that \*doesn't\* bring a lot of pre-conceived baggage to the table. Well, then there is obviously only one logical choice: Chunky Bacon Class! Regards, Michael > **路路路** > > > On Dec 12, 2005, at 0:07, Chad Perrin wrote: > > -- > Michael Ulm > R&D Team > ISIS Information Systems Austria > tel: +43 2236 27551-219, fax: +43 2236 21081 > e-mail: michael.ulm@isis-papyrus.com > Visit our Website: [www.isis-papyrus.com](http://www.isis-papyrus.com) ---
**Author:** ![David\_A\_Black3](https://avatars.discourse-cdn.com/v4/letter/d/6a8cbe/32.png) [@David\_A\_Black3](https://rubytalk.org/u/David_A_Black3)\ **Post date:** [13 December 2005 13:07 UTC](https://rubytalk.org/t/about-class-methods/23105/19 "2005-12-13T13:07:47Z")
Hi -- > > By the way . . . has anyone considered a name like "singular"? What > > about "ad lib" instead of "ad hoc"? > > > > I've gotta say, though, that I'm partial to the descriptor "eigen". > > Well, I'm having a terrible time following the distinction between the indefinite number of flavors of this difficult-to-name type of method, but I do know something about naming things. 馃檪 > > Generally, trying to find an existing term, like 'singleton' or 'ad hoc', is a good thing, because lets somebody bring pre-constructed expectations to the process, hopefully saving them time in learning how this particular thing works. > > Unless, of course, different people have different expectations for that word, or if the thing in question contradicts the expectations in some way. > > If 'simpleton' and 'singleton' are equally applicable to either of two different cases, as somebody suggested earlier, then these will lead people to \*think\* they know what will happen, but there's a 50/50 chance that it will be the other. So that's not a good thing. There appears to be some concern that "ad hoc" implies something much broader (?) than this particular usage actually has. That's not a good thing. > > If you have a situation where none of the existing reasonable terms seem like an adequately non-confusing match, then it's actually much better to use a term that \*doesn't\* bring a lot of pre-conceived baggage to the table. If you create a term that's \*obviously\* meaningless or ambiguous, then the first-time user knows right away that they'll have to look it up, instead of erroneously thinking they know what it does just because of the name. Calling them something like "intral methods", "uni methods", "anonic methods," or "eigenz" is better than using a "real" pre-existing word that is a poor fit. "Hmm. Uni methods. Well, I have a hunch what that might be for, but it isn't immediately obvious. I'll just have to read more about it to find out what they actually do." A couple of problems with that, in this particular case: First, there's an existing term (singleton method/class) that's under review by Matz, with input from the community. That means that calling them "potato-peel classes", or whatever, not only adds confusion but short-circuits a process that's already underway and that promises to result in a decision and clarification. Second, you can't read more about the thing if you don't know what it's called. All this renaming just adds an extra layer of having to learn about the history of ruby-talk, as well as the features of the Ruby language, in order to know what people are talking about in the first place. The advantages of this elude me. I think the community would be well advised not to assume that the world's interest in keeping track of who uses which home-made synonym for "singleton class" is unlimited. David > **路路路** > > On Tue, 13 Dec 2005, Dave Howell wrote: > > > On Dec 12, 2005, at 0:07, Chad Perrin wrote: > > -- > David A. Black > dblack@wobblini.net > > "Ruby for Rails", forthcoming from Manning Publications, April 2006! ---
**Author:** ![Jonathan\_zjll9](https://avatars.discourse-cdn.com/v4/letter/j/858c86/32.png) [@Jonathan\_zjll9](https://rubytalk.org/u/Jonathan_zjll9)\ **Post date:** [14 December 2005 02:40 UTC](https://rubytalk.org/t/about-class-methods/23105/20 "2005-12-14T02:40:20Z")
Dave Howell wrote: > Generally, trying to find an existing term, like 'singleton' or 'ad > hoc', is a good thing, because lets somebody bring pre-constructed > expectations to the process, hopefully saving them time in learning how > this particular thing works. I believe, and there is a slight chance that I'm wrong, that the terms simpleton and singleton are synonymous. --J > **路路路** > > -- > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C). [Next page](https://rubytalk.org/t/about-class-methods/23105.md?page=2)