Saving an active record, in what order are the associated objects saved?
- by Bryan
In rails, when saving an active_record object, its associated objects will be saved as well. But has_one and has_many association have different order in saving objects.
I have three simplified models:
class Team < ActiveRecord::Base
has_many :players
has_one :coach
end
class Player < ActiveRecord::Base
belongs_to :team
validates_presence_of :team_id
end
class Coach < ActiveRecord::Base
belongs_to :team
validates_presence_of :team_id
end
I expected that when team.save is called, team should be saved before its associated coach and players.
I use the following code to test these models:
t = Team.new
team.coach = Coach.new
team.save!
team.save! returns true.
But in another test:
t = Team.new
team.players << Player.new
team.save!
team.save! gives the following error:
> ActiveRecord::RecordInvalid:
> Validation failed: Players is invalid
I figured out that team.save! saves objects in the following order: 1) players, 2) team, and 3) coach. This is why I got the error: When a player is saved, team doesn't yet have a id, so validates_presence_of :team_id fails in player.
Can someone explain to me why objects are saved in this order? This seems not logical to me.
