Rails saving many to many only saves one association - ruby-on-rails

Question

I have the following relationship in my models:
class ClientProfile < ActiveRecord::Base
has_many :client_folders
has_many :folders, through: :client_folders
accepts_nested_attributes_for :folders
end
class Folder < ActiveRecord::Base
has_many :client_folders
has_many :client_profiles, through: :client_folders
end
class ClientFolder < ActiveRecord::Base
belongs_to :client_profile
belongs_to :folder
end
I have the relationships built up in controller:
#client_profile = ClientProfile.new
2.times do |i|
#folder = Folder.new(folder_name: "folder #{i}")
#client_profile.folders << #folder
end
I have the following fields_for associations created in view:
<%= form_for #client_profile do |f| %>
...
<%= f.fields_for :folders do |folder_builder| %>
<%= folder_builder.text_field :some_column %>
...
<% end %>
<% end %>
And the create action:
def create
#client_profile = ClientProfile.new client_profile_params
if #client_profile.save
...
else
...
end
end
When I save the association, it does create the client_profile as well as the two folders, and the join model ClientFolder is correctly created twice. However in both ClientFolders created, it only has the folder_id filled in. The client_profile_id is left null.
One solution I tried is adding the following to client_profile to ensure it saves the join model relation correctly:
def folders_attributes=(params)
if params["0"][:id].nil?
params.values.each do |v|
f = Folder.new v
self.folders << f
end
end
end
But this raises the following exception when saving:
NoMethodError - undefined method `each' for #<ClientFolder:0x007fd364743d78>:
activemodel (4.1.5) lib/active_model/attribute_methods.rb:435:in `method_missing'
activerecord (4.1.5) lib/active_record/attribute_methods.rb:208:in `method_missing'
activerecord (4.1.5) lib/active_record/autosave_association.rb:349:in `save_collection_association'
activerecord (4.1.5) lib/active_record/autosave_association.rb:186:in `block in add_autosave_association_callbacks'
activerecord (4.1.5) lib/active_record/autosave_association.rb:157:in `instance_eval'
activerecord (4.1.5) lib/active_record/autosave_association.rb:157:in `block in define_non_cyclic_method'
activesupport (4.1.5) lib/active_support/callbacks.rb:424:in `block in make_lambda'
activesupport (4.1.5) lib/active_support/callbacks.rb:221:in `call'
activesupport (4.1.5) lib/active_support/callbacks.rb:221:in `block in halting_and_conditional'
activesupport (4.1.5) lib/active_support/callbacks.rb:215:in `call'
activesupport (4.1.5) lib/active_support/callbacks.rb:215:in `block in halting_and_conditional'
activesupport (4.1.5) lib/active_support/callbacks.rb:215:in `call'
activesupport (4.1.5) lib/active_support/callbacks.rb:215:in `block in halting_and_conditional'
activesupport (4.1.5) lib/active_support/callbacks.rb:215:in `call'
activesupport (4.1.5) lib/active_support/callbacks.rb:215:in `block in halting_and_conditional'
activesupport (4.1.5) lib/active_support/callbacks.rb:86:in `call'
activesupport (4.1.5) lib/active_support/callbacks.rb:86:in `run_callbacks'
activerecord (4.1.5) lib/active_record/callbacks.rb:306:in `_create_record'
activerecord (4.1.5) lib/active_record/timestamp.rb:57:in `_create_record'
activerecord (4.1.5) lib/active_record/persistence.rb:482:in `create_or_update'
activerecord (4.1.5) lib/active_record/callbacks.rb:302:in `block in create_or_update'
activesupport (4.1.5) lib/active_support/callbacks.rb:113:in `call'
activesupport (4.1.5) lib/active_support/callbacks.rb:113:in `call'
activesupport (4.1.5) lib/active_support/callbacks.rb:166:in `block in halting'
activesupport (4.1.5) lib/active_support/callbacks.rb:166:in `call'
activesupport (4.1.5) lib/active_support/callbacks.rb:166:in `block in halting'
activesupport (4.1.5) lib/active_support/callbacks.rb:166:in `call'
activesupport (4.1.5) lib/active_support/callbacks.rb:166:in `block in halting'
activesupport (4.1.5) lib/active_support/callbacks.rb:86:in `call'
activesupport (4.1.5) lib/active_support/callbacks.rb:86:in `run_callbacks'
activerecord (4.1.5) lib/active_record/callbacks.rb:302:in `create_or_update'
activerecord (4.1.5) lib/active_record/persistence.rb:103:in `save'
activerecord (4.1.5) lib/active_record/validations.rb:51:in `save'
activerecord (4.1.5) lib/active_record/attribute_methods/dirty.rb:21:in `save'
activerecord (4.1.5) lib/active_record/transactions.rb:268:in `block (2 levels) in save'
activerecord (4.1.5) lib/active_record/transactions.rb:329:in `block in with_transaction_returning_status'
activerecord (4.1.5) lib/active_record/connection_adapters/abstract/database_statements.rb:201:in `block in transaction'
activerecord (4.1.5) lib/active_record/connection_adapters/abstract/database_statements.rb:209:in `within_new_transaction'
activerecord (4.1.5) lib/active_record/connection_adapters/abstract/database_statements.rb:201:in `transaction'
activerecord (4.1.5) lib/active_record/transactions.rb:208:in `transaction'
activerecord (4.1.5) lib/active_record/transactions.rb:326:in `with_transaction_returning_status'
activerecord (4.1.5) lib/active_record/transactions.rb:268:in `block in save'
Someone else recommended to add the join model association:
accepts_nested_attributes_for :client_folders
But it doesn't make sense to do that, since I am not using client_folders at all in the form. When I use fields_for :folders in form, it should be intelligent enough to save the join model properly in create.
How can I resolve this issue?

Answer 1

I discovered the problem.
I had defined the relation twice in the model:
has_many :client_folders
has_one :client_folders, :class_name => 'ClientFolder', :foreign_key => :folder_id
When I removed that has_one, everything worked accordingly.