Rails order by in associated model

Question

I have two models in a has_many relationship such that Log has_many Items. Rails then nicely sets up things like: some_log.items which returns all of the associ

Answer 1

Either of these should work:

Item.all(:conditions => {:log_id => some_log.id}, :order => "some_col DESC")
some_log.items.all(:order => "some_col DESC")

Answer 2

set default_scope in your model class

class Item < ActiveRecord::Base
  default_scope :order => "some_col DESC"
end

This will work

Answer 3

order by direct relationship has_many :model

is answered here by Aaron

order by joined relationship has_many :modelable, through: :model

class Tournament
  has_many :games # this is a join table
  has_many :teams, through: :games

  # order by :name, assuming team has this column
  def teams
    super.order(:name)
  end
end

Tournament.first.teams # are returned ordered by name

Answer 4

There are multiple ways to do this:

If you want all calls to that association to be ordered that way, you can specify the ordering when you create the association, as follows:

class Log < ActiveRecord::Base
  has_many :items, :order => "some_col DESC"
end

You could also do this with a named_scope, which would allow that ordering to be easily specified any time Item is accessed:

class Item < ActiveRecord::Base
  named_scope :ordered, :order => "some_col DESC"
end

class Log < ActiveRecord::Base
  has_many :items
end

log.items # uses the default ordering
log.items.ordered # uses the "some_col DESC" ordering

If you always want the items to be ordered in the same way by default, you can use the (new in Rails 2.3) default_scope method, as follows:

class Item < ActiveRecord::Base
  default_scope :order => "some_col DESC"
end

Answer 5

rails 4.2.20 syntax requires calling with a block:

class Item < ActiveRecord::Base
  default_scope { order('some_col DESC') }
end

This can also be written with an alternate syntax:

default_scope { order(some_col: :desc) }