# Named parameters idiom **URL:** \ **Category:** Ruby\ **Created:** [November 6, 2007, 12:47pm UTC](https://www.ruby-forum.com/t/named-parameters-idiom/119365 "2007-11-06T12:47:15Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![fernan2](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/c5a1d2/32.png) [@fernan2](https://www.ruby-forum.com/u/fernan2)\ **Post date:** [November 6, 2007, 12:47pm UTC](https://www.ruby-forum.com/t/named-parameters-idiom/119365/1 "2007-11-06T12:47:15Z")
Hi people, I often see hashes used as a form of named parameters, with some variations. However, I couldn’t find the idiom properly explained anywhere. I’m just missing it? Where is it? Would anyone like to explain the idiom here? specially, when, why and how it is recommended. It worries me that while it adds clarity at the point of call, it takes it away at the function defintion point, so I haven’t dare to use it yet. TIA ---
**Author:** ![fernan2](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/c5a1d2/32.png) [@fernan2](https://www.ruby-forum.com/u/fernan2)\ **Post date:** [November 6, 2007, 2:19pm UTC](https://www.ruby-forum.com/t/named-parameters-idiom/119365/2 "2007-11-06T14:19:17Z")
Hi – On Tue, 6 Nov 2007, Fernando C. wrote: > Hi people, > > I often see hashes used as a form of named parameters, with some variations. > However, I couldn’t find the idiom properly explained anywhere. > I’m just missing it? Where is it? > > Would anyone like to explain the idiom here? specially, when, why and how it > is recommended. You pass a hash to the method, using pre-determined keys that serve as pseudo-keywords. For example: enroll(:applicant =\> person, :date =\> Time.now, :status =\> “admin”) (Notice that I don’t have to wrap the hash in curly braces. The rule is that if a hash is the last thing in the argument list, you can drop the braces.) The “why” part of it is that it gives the caller a way to (a) document what the arguments are for a little bit, and (b) not worry about the order of arguments, since hash keys can appear in any order. > It worries me that while it adds clarity at the point of call, it takes it > away at the function defintion point, so I haven’t dare to use it yet. It’s a bit wordier than plain local variable names, but usually worth the trade-off if you think it’s important to make things a little easier for the caller. Note that in 1.9, my example could be written as: enroll(applicant: person, date: Time.now, status: “admin”) David ---
**Author:** ![fernan2](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/c5a1d2/32.png) [@fernan2](https://www.ruby-forum.com/u/fernan2)\ **Post date:** [November 6, 2007, 2:56pm UTC](https://www.ruby-forum.com/t/named-parameters-idiom/119365/3 "2007-11-06T14:56:41Z")
David A. Black wrote: > > Would anyone like to explain the idiom here? specially, when, why > > and how it is recommended. > > You pass a hash to the method, using pre-determined keys that serve as > pseudo-keywords. For example: > > enroll(:applicant =\> person, :date =\> Time.now, :status =\> “admin”) OK then enroll would just look like this: def enroll ( args = {} ) args[:applicant] # etc end right? > (Notice that I don’t have to wrap the hash in curly braces. The rule > is that if a hash is the last thing in the argument list, you can drop > the braces.) Ha… I missed this. > The “why” part of it is that it gives the caller a way to (a) document > what the arguments are for a little bit, and (b) not worry about the > order of arguments, since hash keys can appear in any order. Ya, it looks more clear to the caller. I often see a mix of unnamed and named parameters in the same function. Is there an implicit convention to use named params for optional arguments mainly? > enroll(applicant: person, date: Time.now, status: “admin”) Now that’s cool. How would the enroll() function definition look in 1.9? ---
**Author:** ![fernan2](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/c5a1d2/32.png) [@fernan2](https://www.ruby-forum.com/u/fernan2)\ **Post date:** [November 6, 2007, 6:08pm UTC](https://www.ruby-forum.com/t/named-parameters-idiom/119365/4 "2007-11-06T18:08:08Z")
On Nov 6, 2007, at 4:46 AM, Fernando C. wrote: > It worries me that while it adds clarity at the point of call, it > takes it away at the function defintion point, so I haven’t dare to > use it yet. def another\_idiom options = { :can =\> ‘be enumerated here for clarity’, :if =\> ‘you want the signature to be more declarative’ } end cheers. a @ [http://codeforpeople.com/](http://codeforpeople.com/) ---
**Author:** ![fernan2](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/c5a1d2/32.png) [@fernan2](https://www.ruby-forum.com/u/fernan2)\ **Post date:** [November 6, 2007, 6:37pm UTC](https://www.ruby-forum.com/t/named-parameters-idiom/119365/5 "2007-11-06T18:37:23Z")
ara.t.howard wrote: > Good point Best Fernando ---
**Author:** ![fernan2](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/c5a1d2/32.png) [@fernan2](https://www.ruby-forum.com/u/fernan2)\ **Post date:** [November 6, 2007, 4:59pm UTC](https://www.ruby-forum.com/t/named-parameters-idiom/119365/6 "2007-11-06T16:59:04Z")
On 11/6/07, David A. Black [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > The “why” part of it is that it gives the caller a way to (a) document > what the arguments are for a little bit, and (b) not worry about the > order of arguments, since hash keys can appear in any order. ## And (c) it allows for an arbitrary number of truly optional arguments which are order independent. Which is really just amplifying on (b). Rick DeNatale My blog on Ruby [http://talklikeaduck.denhaven2.com/](http://talklikeaduck.denhaven2.com/)