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[Q] How can I ask to which module a method belongs to?

Markus Gaelli

9/1/2006 7:48:00 AM

Hi List,

more questions from a Ruby-Newbie...

Sam Roberts from Ruby-Core answered to my original question:
>> I am aware of Singleton Methods, but as they can extend instances,
>> (how) can I extend classes without changing their original class
>> definition in Ruby?
>>
>
> This is probably best posted to ruby-talk, not ruby-core, folks would
> likely be quite interested.
>
> classes are "open" in ruby, you can add methods as you wish.
>
> irb(main):001:0> s = "hi"
> => "hi"
> irb(main):002:0> class String; def this(opt) puts(self+opt) end end
> => nil
> irb(main):003:0> s.this(" that")
> hi that
> => nil
> irb(main):004:0> "bye".this(" that")
> bye that
> => nil
>
> Cheers,
> Sam

That is good news to me. But now I wonder, if and how I can ask e.g.
String#this(opt) in which module it is defined.
Any ideas?

Cheers,

Markus
2 Answers

Rick DeNatale

9/1/2006 9:29:00 PM

0

On 9/1/06, Markus Gaelli <gaelli@emergent.de> wrote:
> Hi List,
>
> more questions from a Ruby-Newbie...
>
> Sam Roberts from Ruby-Core answered to my original question:
> >> I am aware of Singleton Methods, but as they can extend instances,
> >> (how) can I extend classes without changing their original class
> >> definition in Ruby?
> >>
> >
> > This is probably best posted to ruby-talk, not ruby-core, folks would
> > likely be quite interested.
> >
> > classes are "open" in ruby, you can add methods as you wish.
> >
> > irb(main):001:0> s = "hi"
> > => "hi"
> > irb(main):002:0> class String; def this(opt) puts(self+opt) end end
> > => nil
> > irb(main):003:0> s.this(" that")
> > hi that
> > => nil
> > irb(main):004:0> "bye".this(" that")
> > bye that
> > => nil
> >
> > Cheers,
> > Sam
>
> That is good news to me. But now I wonder, if and how I can ask e.g.
> String#this(opt) in which module it is defined.

First note, that a method can be defined in a module or a class, and
that a class is a kind of module.

I haven't tested this extensively but I think it works. It searches
for a method name in a class the same way that methods are found at
runtime, at each level of the class hierarchy, the class is searched,
then any modules that class includes in the reverse order they were
included. This code depends on Module#included_modules giving it's
result in the right order, which a few quick tests seems to indicate:
module A
end
module B
end
module C
include B
include A
end

C.included_modules => [A, B]
module D
include A
include B
end
D.included_modules => [B, A]

Okay so here's my code:

class Module
def module_defining(method_name)
method_name = method_name.to_s
return self if instance_methods(false).include?(method_name)
included_modules.each do |mixin|
answer = mixin.module_defining(method_name)
return answer if answer
end
nil
end
end

class Class
def module_defining(method_name)
answer = super
return answer if answer
return superclass.module_defining(method_name) if superclass
end
end

irb(main):001:0> load 'moddefining.rb'
=> true
irb(main):002:0> String.module_defining('==')
=> String
irb(main):003:0> String.module_defining('id')
=> Kernel
irb(main):004:0> String.module_defining('map')
=> Enumerable



--
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denh...

Lee Flynn

10/28/2009 3:52:00 AM

0

On 10/18/2009 6:01 PM, Jasmine wrote:
> On Oct 10, 2:52 pm, Lee<lucidre...@att.net> wrote:
>> On 10/7/2009 2:12 PM, Jasmine wrote:
>>
>>> does the Almighty speak to us and if so, how? all thoughts are
>>> appreciated...
>>
>>> Peace
>>
>> Hi Jasmine,
>>
>> The Almighty reaches me through the language of
>> heart-wrenching compassion amidst conditions that
>> I know to be Handled despite all appearance, and
>> through experiences of profound awe and gratitude
>> for life's bounty and perfect orchestration.
>>
>> So, direct communication? No. But frequently
>> through intense feelings as well as through
>> signs and messages such as 'inexplicable'
>> synchronicities.
>>
>> You might find Robert Perry's new book "Signs" to
>> be an interesting read in this regard. Sheryl has
>> been recently notifying us of her review of the
>> book, and has offered a recording of her interview
>> with Perry from her website. I haven't seen the
>> book yet, myself.
>>
>> Hope you had a lovely summer, Jasmine
>>
>> ~ Lee
>
> thanks...hopefully I will lift my head out of the drudgery for a
> breath to read again, Perry's book just might make it to my night
> stand. sorry but I am terribly miserable lately.
>
> All apologies for the ick typed out. At the same time, thank you all
> for your responses. many of the words shared contribute to a greater
> understanding of the human condition...

Thinking of you Jasmine, and wishing you well.
Love to you, ~ Lee