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comp.lang.ruby

item order in Object#methods

Andrea Fazzi

12/18/2006 3:09:00 PM

Hi all,

please consider two files: init.rb and init_2.rb. In init.rb put this
bunch of code:

module Foo
def init
self.methods.collect { |meth| meth if meth =~ /init_/ }.compact.each
do |init_meth|
self.send(init_meth.to_sym)
end
end
end

class Bar
include Foo
def initialize
init
end
def init_1
puts "Method init_1 called!"
end
end

class Bar
def init_2
puts "Method init_2 called!"
end
def init_3
puts "Method init_3 called!"
end
def init_4
puts "Method init_4 called!"
end
end

Then in init_2.rb put another bunch of code:

require 'init'

class Bar
def init_5
puts "Method init_5 called!"
end
def init_6
puts "Method init_6 called!"
end
end

Bar.new

Now execute init_2.rb. I get the following result:

Method init_4 called!
Method init_5 called!
Method init_6 called!
Method init_1 called!
Method init_2 called!
Method init_3 called!

but I expected:

Method init_1 called!
Method init_2 called!
Method init_3 called!
Method init_4 called!
Method init_5 called!
Method init_6 called!

So, which is the sort criteria of the array returned by Object#methods?

Thanks a lot!
Andrea
3 Answers

Rob Biedenharn

12/18/2006 3:20:00 PM

0


On Dec 18, 2006, at 10:08 AM, Andrea Fazzi wrote:

> Hi all,
>
> please consider two files: init.rb and init_2.rb. In init.rb put
> this bunch of code:
>
> module Foo
> def init
> self.methods.collect { |meth| meth if meth =~ /
> init_/ }.compact.each do |init_meth|
> self.send(init_meth.to_sym)
> end
> end
> end
>
> ...
>
> So, which is the sort criteria of the array returned by
> Object#methods?
>
> Thanks a lot!
> Andrea

If it's important, why not sort them first:
self.methods.sort.collect { ... }

-Rob

Rob Biedenharn http://agileconsult...
Rob@AgileConsultingLLC.com

Andrea Fazzi

12/18/2006 3:33:00 PM

0

Rob Biedenharn wrote:
>
> If it's important, why not sort them first:
> self.methods.sort.collect { ... }
>


Because I'm interested to the methods' definition order inside the class
not to the alphabetical order of methods' name. The names init_1,
init_2, etc. were just an example.

Andrea

Rob Biedenharn

12/18/2006 4:17:00 PM

0

On Dec 18, 2006, at 10:32 AM, Andrea Fazzi wrote:
> Rob Biedenharn wrote:
>>
>> If it's important, why not sort them first:
>> self.methods.sort.collect { ... }
>
> Because I'm interested to the methods' definition order inside the
> class not to the alphabetical order of methods' name. The names
> init_1, init_2, etc. were just an example.
>
> Andrea

I'd not be surprised to hear (from someone who actually knows rather
than speculates ;-) that the methods are stored in a hash and there
is no definite order to them. As for the order in which they were
defined, that's just the order in which they were encountered.

When I run the code from your first message:
rab:ruby $ ruby init_2.rb
Method init_3 called!
Method init_4 called!
Method init_5 called!
Method init_6 called!
Method init_1 called!
Method init_2 called!

It's not even the same order as yours (although it is consistent when
I run it multiple times). If the lookup is really hash-based,
defining other methods could "shuffle" these around if the underlying
hash table was expanded. (I'm using "hash" in its algorithmic sense,
not a Ruby class.)

-Rob

Rob Biedenharn http://agileconsult...
Rob@AgileConsultingLLC.com