Item order in Object#methods

ruby-talk
1

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

2

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

-Rob

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

···

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

3

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

4

I'd not be surprised to hear (from someone who actually knows rather than speculates :wink: 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://agileconsultingllc.com
Rob@AgileConsultingLLC.com

···

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