I have models like this:
class Member
belongs_to :team, class_name: 'Team'
end
class Team
has_many :members, foreign_key: :team_id
end
Database has all the columns needed.
When I do: t = Team.new m = Member.new
m.team = team
m.save!
#some other code
t.save!
team_id field is present most of the times but is absent sometimes in the database. I saw in active record documentation that belongs to association is not saved. This looks like a race condition to me but I want to understand why it might happen.
Thanks in advance!
Always create associated objects through the association. That means that you should do the following:
t = Team.create!
m = t.members.create!
This is described in greater detail in the guide for Active Record Associations.
You asked why the example you provided works sometimes but not others. I cannot replicate the problems that you're seeing. It is probably something specific to your implementation or practices that are not shared in your question. Here is how I verified that the issue does not occur.
First, create the Rails app, its associations, its database, and then start the Rails console:
rails new tester
cd tester
rails generate model Team
rails generate model Member team:belongs_to
sed -i '' 's/end/ has_many :members\'$'\nend/' app/models/team.rb
rake db:migrate
rails console
Now create one thousand teams with an associated member, and if the fields are not appropriately set then raise an exception:
1000.times do
t = Team.create!
m = t.members.create!
raise unless m.team_id && m.team_id == t.id
end
Or alternatively, using .new and .save!:
1000.times do
t = Team.new
m = t.members.new
m.save!
raise unless m.team_id && m.team_id == t.id
end
No exception is raised, so by creating in this manner you can be assured that it will work properly.