# Method declaration question **URL:** \ **Category:** Rails\ **Created:** [March 5, 2008, 11:43pm UTC](https://www.ruby-forum.com/t/method-declaration-question/131091 "2008-03-05T23:43:21Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![dino\_d](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b5ac83/32.png) [@dino\_d](https://www.ruby-forum.com/u/dino_d)\ **Post date:** [March 5, 2008, 11:43pm UTC](https://www.ruby-forum.com/t/method-declaration-question/131091/1 "2008-03-05T23:43:21Z")
Hi- In auto\_complete, a method is declared as follows: def auto\_complete\_for(object, method, options = {}) Does the second argument mean I can send anything I want to this method after I send ‘object’? If so, shouldn’t I be able to call it like this: auto\_complete\_for(something,:test =\> “person”) ? I try exactly this and get Unknown key(s): Can someone illuminate me on declaring “something = {}” as an argument and how you call that method with passing in bonus arguments? Thanks, Dino ---
**Author:** ![dino\_d](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b5ac83/32.png) [@dino\_d](https://www.ruby-forum.com/u/dino_d)\ **Post date:** [March 6, 2008, 12:03am UTC](https://www.ruby-forum.com/t/method-declaration-question/131091/2 "2008-03-06T00:03:20Z")
Hi – On Wed, 5 Mar 2008, dino d. wrote: > If so, shouldn’t I be able to call it like this: > > auto\_complete\_for(something,:test =\> “person”) ? > > I try exactly this and get > > Unknown key(s): > > Can someone illuminate me on declaring “something = {}” as an argument > and how you call that method with passing in bonus arguments? Given this: def m(a, b, c = {}) a and b are required arguments, and have to come in that order. c is an optional argument; if you don’t provide it, c will be assigned an empty hash (or whatever you put there as the default value). In your case, the hash { :test =\> “person” } is being assigned to method, and c is an empty hash. Basically, you’re missing an argument. David > Thanks, > Dino > > > – Upcoming Rails training from David A. Black and Ruby Power and Light: ADVANCING WITH RAILS, April 14-17 2008, New York City CORE RAILS, June 24-27 2008, London (Skills Matter) See [http://www.rubypal.com](http://www.rubypal.com) for details. Berlin dates coming soon! ---
**Author:** ![dino\_d](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b5ac83/32.png) [@dino\_d](https://www.ruby-forum.com/u/dino_d)\ **Post date:** [March 6, 2008, 1:07am UTC](https://www.ruby-forum.com/t/method-declaration-question/131091/3 "2008-03-06T01:07:15Z")
Thanks for the reply. Sorry, I typed my original post too fast. This is the declaration: > > def auto\_complete\_for(object, method, options = {}) My call to the method is: auto\_complete\_for :story, :tag\_holder, :foreign =\> ‘tag’ and this usage throws this error: ArgumentError (Unknown key(s): foreign): Any idea why? Thanks, and sorry for the rushed post. Dino ---
**Author:** ![dino\_d](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b5ac83/32.png) [@dino\_d](https://www.ruby-forum.com/u/dino_d)\ **Post date:** [March 6, 2008, 1:55am UTC](https://www.ruby-forum.com/t/method-declaration-question/131091/4 "2008-03-06T01:55:55Z")
On 3/5/08, dino d. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > auto\_complete\_for :story, :tag\_holder, :foreign =\> ‘tag’ > > and this usage throws this error: > > ArgumentError (Unknown key(s): foreign): > > Any idea why? > > Thanks, and sorry for the rushed post. Well auto\_complete\_for is taking the options hash, which in your case is {:foreign =\> ‘tag’} and merging it into the options passed to ActiveRecord::Base#find, so the following effective expression gets invoked: ``` Story.find(:all, :conditions => [ "LOWER(tag_holder) LIKE ?", '%' ``` - params[:story][:tag\_holder].downcase + ‘%’ ], :order =\> “#{tag\_holder} ASC”, :limit =\> 10, :foreign =\> ‘tag’) And ActiveRecord::Find is rejecting :foreign since it’s not a valid option. – Rick DeNatale My blog on Ruby [http://talklikeaduck.denhaven2.com/](http://talklikeaduck.denhaven2.com/) ---
**Author:** ![dino\_d](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b5ac83/32.png) [@dino\_d](https://www.ruby-forum.com/u/dino_d)\ **Post date:** [March 6, 2008, 1:43am UTC](https://www.ruby-forum.com/t/method-declaration-question/131091/5 "2008-03-06T01:43:36Z")
Hi – On Wed, 5 Mar 2008, dino d. wrote: > and this usage throws this error: > > ArgumentError (Unknown key(s): foreign): > > Any idea why? The options hash gets merged into the find options for a database query, so it has to be something that’s meaningful in that context. You could, for example, put :limit =\> 20, which would override the default limit of 10. But :foreign =\> ‘tag’ doesn’t mean anything in an ActiveRecord query. David – Upcoming Rails training from David A. Black and Ruby Power and Light: ADVANCING WITH RAILS, April 14-17 2008, New York City CORE RAILS, June 24-27 2008, London (Skills Matter) See [http://www.rubypal.com](http://www.rubypal.com) for details. Berlin dates coming soon! ---
**Author:** ![dino\_d](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b5ac83/32.png) [@dino\_d](https://www.ruby-forum.com/u/dino_d)\ **Post date:** [March 6, 2008, 2:22am UTC](https://www.ruby-forum.com/t/method-declaration-question/131091/6 "2008-03-06T02:22:17Z")
Thanks for the replies. How do I specify my own hasg? i.e. can a method take two hashes, and if so, how do I specify which hash an option goes into whne called? ex) def mymethod(a,b, c={}, d={}) how do i specify the call? Thanks again, Dino ---
**Author:** ![dino\_d](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b5ac83/32.png) [@dino\_d](https://www.ruby-forum.com/u/dino_d)\ **Post date:** [March 6, 2008, 2:33am UTC](https://www.ruby-forum.com/t/method-declaration-question/131091/7 "2008-03-06T02:33:25Z")
Hi – On Wed, 5 Mar 2008, dino d. wrote: > Thanks for the replies. How do I specify my own hasg? i.e. can a > method take two hashes, and if so, how do I specify which hash an > option goes into whne called? > > ex) > > def mymethod(a,b, c={}, d={}) > > how do i specify the call? What you’ve got there are two required arguments and two optional arguments. If you call that method with all four args specified, you’d do: mymethod(1,2, { :m =\> “n” }, :x =\> “y”) That will give the following assignments: a 1 b 2 c { :m =\> “n” } d { :x =\> “y” } Ruby has the special rule that if a hash is the last thing in the argument list, you can leave off the curly braces. But the third argument, in this scenario, is _not_ the last argument, so it needs its curly braces. Otherwise it is, as I think you’ve surmised, impossible to tell where one hash is supposed to end and the next one begin. David – Upcoming Rails training from David A. Black and Ruby Power and Light: ADVANCING WITH RAILS, April 14-17 2008, New York City CORE RAILS, June 24-27 2008, London (Skills Matter) See [http://www.rubypal.com](http://www.rubypal.com) for details. Berlin dates coming soon! ---
**Author:** ![dino\_d](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b5ac83/32.png) [@dino\_d](https://www.ruby-forum.com/u/dino_d)\ **Post date:** [March 6, 2008, 3:16am UTC](https://www.ruby-forum.com/t/method-declaration-question/131091/8 "2008-03-06T03:16:48Z")
> Ruby has the special rule that if a hash is the last thing in the > argument list, you can leave off the curly braces. _This_ is a critical missing piece of knowledge for me. Thanks so much. Btw, I’ve found learnng basic rails pretty easy, but learning intermediate rails extremely difficult because I can’t find a good book to take me there. Can you recommend one? How did you get from beginner to intermediate to expert? Thanks, Dino ---
**Author:** ![dino\_d](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b5ac83/32.png) [@dino\_d](https://www.ruby-forum.com/u/dino_d)\ **Post date:** [March 6, 2008, 1:46pm UTC](https://www.ruby-forum.com/t/method-declaration-question/131091/9 "2008-03-06T13:46:32Z")
Hi – On Wed, 5 Mar 2008, dino d. wrote: > > Ruby has the special rule that if a hash is the last thing in the > > argument list, you can leave off the curly braces. > > _This_ is a critical missing piece of knowledge for me. Thanks so > much. Btw, I’ve found learnng basic rails pretty easy, but learning > intermediate rails extremely difficult because I can’t find a good > book to take me there. Can you recommend one? How did you get from > beginner to intermediate to expert? The key for me was that I had been using Ruby for almost four years before Rails was even released, and that I understood automatically that writing a Rails application is actually a process of writing lots of little Ruby programs. There’s nothing secret about this, of course, though sometimes the Rails magic and high-level techniques can make it seem like you’re just floating on an abstract layer where you don’t really have to think about what the syntax actually means or what the objects are doing. As you see from the case of the hash argument idiom, that’s not true – at least not if you want to get past that beginning stage. As for books, there’s “Ruby for Rails” (by me), which is a Ruby intro/guide with topics selected with an eye toward the Rails developer. The Rails examples in it are based on Rails 1.something, so I wouldn’t recommend it as a single source of Rails knowledge (which wasn’t its purpose anyway), but the Ruby is 1.8 and therefore still the Ruby that almost all Rails developers use. There’s also “The Rails Way”, by Obie F., which I think would be a very good resource. There are probably others; I’m not fully up to date these days on the book scene, as there are so many – which is great, but makes it hard to keep up! David – Upcoming Rails training from David A. Black and Ruby Power and Light: ADVANCING WITH RAILS, April 14-17 2008, New York City CORE RAILS, June 24-27 2008, London (Skills Matter) See [http://www.rubypal.com](http://www.rubypal.com) for details. Berlin dates coming soon!