# Getting method parameters in specified order **URL:** \ **Category:** Ruby\ **Created:** [December 13, 2007, 7:46am UTC](https://www.ruby-forum.com/t/getting-method-parameters-in-specified-order/122985 "2007-12-13T07:46:19Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Chintana\_W](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/c89c15/32.png) [@Chintana\_W](https://www.ruby-forum.com/u/Chintana_W)\ **Post date:** [December 13, 2007, 7:46am UTC](https://www.ruby-forum.com/t/getting-method-parameters-in-specified-order/122985/1 "2007-12-13T07:46:19Z")
Hi, If I declare a function that expects 3 arguments, def bar(x, y, z) … end and later, if I have the function name in a string, is there a way to get the parameter names using reflection in Ruby? Something similar to the following PHP snippet, $a = new ReflectionFunction(“function\_name”); $a-\>getParameters(); Thanks in advance, Bye, ``` -Chintana ``` ---
**Author:** ![Chintana\_W](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/c89c15/32.png) [@Chintana\_W](https://www.ruby-forum.com/u/Chintana_W)\ **Post date:** [December 13, 2007, 2:07pm UTC](https://www.ruby-forum.com/t/getting-method-parameters-in-specified-order/122985/2 "2007-12-13T14:07:23Z")
I think we cant do more than this: irb(main):001:0\> def test(a, b, c) irb(main):002:1\> end =\> nil irb(main):003:0\> method(:test).arity =\> 3 ---
**Author:** ![Chintana\_W](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/c89c15/32.png) [@Chintana\_W](https://www.ruby-forum.com/u/Chintana_W)\ **Post date:** [December 13, 2007, 4:46pm UTC](https://www.ruby-forum.com/t/getting-method-parameters-in-specified-order/122985/3 "2007-12-13T16:46:04Z")
On Dec 13, 2007 6:36 PM, Bernardo Monteiro R. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > I think we cant do more than this: > > irb(main):001:0\> def test(a, b, c) > irb(main):002:1\> end > =\> nil > irb(main):003:0\> method(:test).arity > =\> 3 Thanks Bernardo. Bye, ``` -Chintana ``` ---
**Author:** ![Chintana\_W](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/c89c15/32.png) [@Chintana\_W](https://www.ruby-forum.com/u/Chintana_W)\ **Post date:** [December 13, 2007, 6:56pm UTC](https://www.ruby-forum.com/t/getting-method-parameters-in-specified-order/122985/4 "2007-12-13T18:56:08Z")
On Dec 12, 11:44 pm, Chintana W. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Hi, > > If I declare a function that expects 3 arguments, > > def bar(x, y, z) > … > end > > and later, if I have the function name in a string, is there a way to > get the parameter names using reflection in Ruby? There is not; as Bernardo said, Ruby only allows you to check the arity of the method. I had a need for this, too. (I was working on a project that allowed developers to provide arbitrary Ruby-based plugins, and the GUI of the application needed to expose the methods and their paramters visually.) For that need, I wrote this: [http://phrogz.net/RubyLibs/rdoc/classes/DescribeMethods.html](http://phrogz.net/RubyLibs/rdoc/classes/DescribeMethods.html) ---
**Author:** ![Chintana\_W](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/c89c15/32.png) [@Chintana\_W](https://www.ruby-forum.com/u/Chintana_W)\ **Post date:** [December 14, 2007, 4:23am UTC](https://www.ruby-forum.com/t/getting-method-parameters-in-specified-order/122985/5 "2007-12-14T04:23:00Z")
From: Chintana W. [[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)] # Sent: Thursday, December 13, 2007 11:40 PM # To: ruby-talk ML # Subject: Re: Getting method parameters in specified order # # On Dec 13, 2007 6:36 PM, Bernardo Monteiro R. # [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: # # \> I think we cant do more than this: # \> # \> irb(main):001:0\> def test(a, b, c) # \> irb(main):002:1\> end # \> =\> nil # \> irb(main):003:0\> method(:test).arity # \> =\> 3 not part of ruby itself, but try looking at ruby2ruby kind regards -botp ---
**Author:** ![Chintana\_W](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/c89c15/32.png) [@Chintana\_W](https://www.ruby-forum.com/u/Chintana_W)\ **Post date:** [December 14, 2007, 1:55pm UTC](https://www.ruby-forum.com/t/getting-method-parameters-in-specified-order/122985/6 "2007-12-14T13:55:20Z")
> Forgive the naive thoughts of a ruby ruby… ruby nuby, I meant. heh ---
**Author:** ![Chintana\_W](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/c89c15/32.png) [@Chintana\_W](https://www.ruby-forum.com/u/Chintana_W)\ **Post date:** [December 14, 2007, 9:16am UTC](https://www.ruby-forum.com/t/getting-method-parameters-in-specified-order/122985/7 "2007-12-14T09:16:39Z")
On Dec 14, 2007 8:52 AM, Peña, Botp [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: [snip] Thanks Botp and Phrogz, I’ll look into it. Bye, ``` -Chintana ``` ---
**Author:** ![Chintana\_W](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/c89c15/32.png) [@Chintana\_W](https://www.ruby-forum.com/u/Chintana_W)\ **Post date:** [December 15, 2007, 12:52am UTC](https://www.ruby-forum.com/t/getting-method-parameters-in-specified-order/122985/8 "2007-12-15T00:52:20Z")
Hi~ On Dec 14, 2007, at 4:57 AM, Lloyd L. wrote: > > get the parameter names using reflection in Ruby? Something similar You can accomplish this with the Ruby2Ruby gem. Here is a pastie of some code that can do this for you: [http://pastie.caboo.se/128959](http://pastie.caboo.se/128959) Here is how you can use it: ~/\_merb/merb \> irb -r get\_args.rb > > class Foo > > def hi(a,b,c) > > p a,b,c > > end > > end > > =\> nil > > Foo.instance\_method(:hi).get\_args > > =\> [[:a], [:b], [:c]] Cheers- - Ezra Z. – Founder & Software Architect – removed\_email\_address@domain.invalid – [EngineYard.com](http://EngineYard.com) ---
**Author:** ![Chintana\_W](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/c89c15/32.png) [@Chintana\_W](https://www.ruby-forum.com/u/Chintana_W)\ **Post date:** [December 14, 2007, 1:54pm UTC](https://www.ruby-forum.com/t/getting-method-parameters-in-specified-order/122985/9 "2007-12-14T13:54:28Z")
Chintana W. wrote: > Hi, > > If I declare a function that expects 3 arguments, > > def bar(x, y, z) > … > end > > and later, if I have the function name in a string, is there a way to > get the parameter names using reflection in Ruby? Something similar > to the following PHP snippet, > > $a = new ReflectionFunction(“function\_name”); > $a-\>getParameters(); Forgive the naive thoughts of a ruby ruby, but what if you accepted an array as the parameter? You could use any number of elements and you would always know which is which.