Rails - Jan 2006 - Member.buddies.sort >> undefined method `<=>''

Hi all

I have a model Member that has a habtm relationship to buddies (also 
members).
Now I wanted to sort them using sort, but this ends in an error 
"undefined method <=>"! Where''s the problem here?
Sorry, I''m still
beginning to learn Ruby. ;-)

Thanks
Josh

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On Jan 11, 2006, at 4:01 PM, Joshua Muheim wrote:
> Hi all
>
> I have a model Member that has a habtm relationship to buddies (also
> members).
> Now I wanted to sort them using sort, but this ends in an error
> "undefined method <=>"! Where''s the problem here?
Sorry, I''m still
> beginning to learn Ruby. ;-)
>
> Thanks
> Josh
It sounds like you''re trying to sort ActiveRecord objects, but the  
trouble with that is there is no "right" way to sort them--by first  
name? last name? date at which they were created? backwards?

You have two options: sort them at the database level, or with Ruby.

Database level:

class Member < ActiveRecord::Base
   has_and_belongs_to_many :buddies, :class_name =>
''Member'' ...
etc ..., :sort => ''lastname, firstname''
end

This will fetch your associated ''buddies'' in alphabetical
order
(lastname, ascending) for each Member object.

Alternatively, you can do it in Ruby code like this (probably what  
you tried):

members = Member.find(:all)
sorted = members.sort { |m1, m2| m1.lastname <=> m2.lastname }

This will sort by lastname.  There''s a shortcut method in Ruby 1.8  
called ''sort_by'' as well.  Robby Russell recently posted a
great
article at the oreilly ruby blog (http://www.oreillynet.com/ruby).   
Unfortunately I can''t find his article there, so look here for a copy  
instead: http://swik.net/Ruby/O''Reilly+Ruby+Blog/Sorting+an+Array+of 
+Hashes+with+Ruby+and+Enumerable/bmqu

Duane Johnson
(canadaduane)
http://blog.inquirylabs.com/

Thanks a lot for your answer!

I have done it like that now:

  has_and_belongs_to_many :buddies,
                          :class_name => ''Member'',
                          :join_table =>
''members_have_buddies'',
                          :association_foreign_key =>
''buddy_id'',
                          :sort => ''username''

but I receive an error now:

Unknown key(s): sort

What''s the problem? Thanks. :-)

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Posted via http://www.ruby-forum.com/.

Joshua Muheim wrote:
> Thanks a lot for your answer!
>
> I have done it like that now:
>
>   has_and_belongs_to_many :buddies,
>                           :class_name => ''Member'',
>                           :join_table =>
''members_have_buddies'',
>                           :association_foreign_key =>
''buddy_id'',
>                           :sort => ''username''
>
> but I receive an error now:
>
> Unknown key(s): sort
>
> What''s the problem? Thanks. :-)
>
>   
Try 
  :order => ''username''

// JoNtE

Jonas Montonen wrote:
> Try
>   :order => ''username''
> 
> // JoNtE
Thanks, this works perfectly.

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