From: dblack@...
Date: 2006-12-10T02:39:11+09:00
Subject: Re: Dynamically Create Singleton Method

Hi --

On Sat, 9 Dec 2006, pachl wrote:

> On Dec 9, 6:26 am, dbl...@wobblini.net wrote:
>> On Sat, 9 Dec 2006, pachl wrote:
>>> I'm not sure how to explain what I'm looking for so I will show you:
>>
>>> # this works, but not quite the functionality I need
>>
>>> def simulate_cgi_upload
>>>  class << cgi_file = Tempfile.new('simulate-cgi')
>>>    def content_type() 'image/jpeg' end
>>>  end
>>>  cgi_file
>>> end
>>
>>> # this does NOT work, but has the functionality I need
>>> # i.e.: dynamically defining content_type's return value using
>>> # the argument from simulate_cgi_upload method.
>>
>>> def simulate_cgi_upload(mime_type = 'image/jpeg')
>>>  class << cgi_file = Tempfile.new('simulate-cgi')
>>>    def content_type() mime_type end
>>>  end
>>>  cgi_file
>>> endTry this (or something like it in case I've mistyped anything):
>>
>>    def simulate_cgi_upload(mime_type = 'image/jpeg')
>>      cgi_file = Tempfile.new('simulate-cgi')
>>      (class << cgi_file; self; end).class_eval do
>>        define_method("content_type") { mime_type }
>>      end
>>      cgi_file
>>    end
>
> Excactly what I was looking for; compact and fairly elegant.
>
> Thanks for the very quick response David and good morning to you.

Good morning :-)

It would be more elegant if we had Kernel#singleton_class -- then you
wouldn't have to do the little workaround.  Fingers crossed....


David

-- 
                   David A. Black | dblack@wobblini.net
Author of "Ruby for Rails"   [1] | Ruby/Rails training & consultancy [3]
DABlog (DAB's Weblog)        [2] | Co-director, Ruby Central, Inc.   [4]
[1] http://www.manning.com/black | [3] http://www.rubypowerandlight.com
[2] http://dablog.rubypal.com    | [4] http://www.rubycentral.org