In this example, I create a user with no profile, then later on create a profile for that user. I tried using build with a has_one association but that blew up. The only way I see this working is using has_many. The user is supposed to only have at most one profile.
I have been trying this. I have:
class User < ActiveRecord::Base
has_one :profile
end
class Profile < ActiveRecord::Base
belongs_to :user
end
But when I do:
user.build_profile
I get the error:
ActiveRecord::StatementInvalid: Mysql::Error: Unknown column 'profiles.user_id' in 'where clause': SELECT * FROM `profiles` WHERE (`profiles`.user_id = 4) LIMIT 1
Is there a way in rails to have 0 or 1 association?
The build method signature is different for has_one and has_many associations.
class User < ActiveRecord::Base
has_one :profile
has_many :messages
end
The build syntax for has_many association:
user.messages.build
The build syntax for has_one association:
user.build_profile # this will work
user.profile.build # this will throw error
Read the has_one association documentation for more details.