first_or_create method with embeds_many association in mongoid - ruby-on-rails

Question

I have User model which used for omni-auth authentication. I have set it up so that different providers (like facebook, google accounts ) can be used for signing in. If the email is already in the database while signing up using these providers ,user is signed into that account.
class User
include Mongoid::Document
embeds_many :providers
field :email,type: String, default: ""
end
class Provider
include Mongoid::Document
field :name, type: String
field :uid, type: String
embedded_in :user
end
And I am using from_omniauth method to find user based on the auth info.
def from_omniauth(auth)
user=User.find_by(email: auth.info.email)
return user if user
where(:"providers.name" => auth.provider, :"provider.uid" => auth.uid ).first_or_create do |user|
user.email = auth.info.email
user.password = Devise.friendly_token[0,20]
end
end
But I am getting an error when it cant find a user and tries to create one.
Mongoid::Errors::UnknownAttribute:
message:
Attempted to set a value for 'providers.name' which is not allowed on the model User.
But why does it consider this as a dynamic field generation as I have already defined the associations. I tried find_or_initialize method also but same error.
Can someone help me figure it out. Thanks in advance.

Answer 1

There's some magic going on here.
When you are invoking #first_or_create on the above criteria:
where(:"providers.name" => auth.provider, :"provider.uid" => auth.uid ).first_or_create do |user|
user.email = auth.info.email
user.password = Devise.friendly_token[0,20]
end
This is actually getting de-sugared into something more like this:
found_user_with_provider = where(:"providers.name" => auth.provider, :"provider.uid" => auth.uid ).first
if found_user_with_provider.nil?
new_user = User.new
new_user.set(:"providers.name", auth.provider)
new_user.set(:"providers.uid", auth.uid)
new_user.email = auth.info.email
new_user.password = Devise.friendly_token[0,20]
else
found_user_with_provider.email = auth.info.email
found_user_with_provider.password = Devise.friendly_token[0,20]
end
Notice the attempt to set the value of "provider.name" and "provider.uid" as attributes on the user instance - which isn't actually what you want, and is what Mongoid is complaining about.
You actually probably want something more like this:
def from_omniauth(auth)
user = User.find_by(email: auth.info.email)
return user if user
found_user_with_provider = where(:"providers.name" => auth.provider, :"provider.uid" => auth.uid ).first
if found_user_with_provider
found_user_with_provider.update_attributes!(
:email => auth.info.email,
:password => Devise.friendly_token[0,20]
)
return found_user_with_provider
end
User.create!({
:providers => [
Provider.new({
:name => auth.provider,
:uid => auth.uid
})
],
:email => auth.info.email,
:password => Devise.friendly_token[0,20]
})
end
Of course there's still one more problem, and that's that you are setting a #password attribute on your user instance. Make sure to add:
field :password,type: String, default: ""
To your user model - otherwise you'll get the same complaint about dynamic fields as before - just this time about a different field.