how to get methods via has_one and belongs_to assocation? - ruby-on-rails

Question

I have few weeks experience or close to a month learning on Ruby on Rails. I hope to understand why I can't get methods via associated objects.
I am attempting to get associated objects attached to user instead of stane alone Profile.new e.g. profile with its methods as seen just below.
user.profile.create
user.profile.create!
user.profile.build
instead i get RSpec error messages. NoMethodError:undefined method `build' for nil:NilClass
Thanks kindly in advance
# == Schema Information
#
# Table name: users
#
# id :integer not null, primary key
# email :string(255)
# created_at :datetime not null
# updated_at :datetime not null
#
class User < ActiveRecord::Base
attr_accessible :email
has_one :profile
before_save { |user| user.email = email.downcase }
VALID_EMAIL_REGEX = /\A[\w+\-.]+#[a-z\d\-.]+\.[a-z]+\z/i
validates :email, presence: true, format: { with: VALID_EMAIL_REGEX },
uniqueness: { case_sensitive: false }
end
.
# == Schema Information
#
# Table name: profiles
#
# id :integer not null, primary key
# given_name :string(255)
# surname :string(255)
# user_id :integer
# created_at :datetime not null
# updated_at :datetime not null
#
class Profile < ActiveRecord::Base
attr_accessible :given_name, :surname #, :user_id
belongs_to :user
validates :user_id, presence: true
end
.
smileymike#ubuntu:~/rails_projects/bffmApp$ bundle exec guard
Guard uses Libnotify to send notifications.
Guard is now watching at '/home/smileymike/rails_projects/bffmApp'
Starting Spork for RSpec
Using RSpec
Preloading Rails environment
Loading Spork.prefork block...
Spork is ready and listening on 8989!
Spork server for RSpec successfully started
Guard::RSpec is running, with RSpec 2!
Running all specs
Running tests with args ["--drb", "-f", "progress", "-r", "/home/smileymike/.rvm/gems/ruby-1.9.3-p194/gems/guard-rspec-0.7.2/lib/guard/rspec/formatters/notification_rspec.rb", "-f", "Guard::RSpec::Formatter::NotificationRSpec", "--out", "/dev/null", "--failure-exit-code", "2", "spec"]...
......FFFFFFFF...............
Failures:
1) Profile
Failure/Error: before { #profile = user.profile.build(given_name: "Michael", surname: "Colin") }
NoMethodError:
undefined method `build' for nil:NilClass
# ./spec/models/profile_spec.rb:23:in `block (2 levels) in <top (required)>'
2) Profile
Failure/Error: before { #profile = user.profile.build(given_name: "Michael", surname: "Colin") }
NoMethodError:
undefined method `build' for nil:NilClass
# ./spec/models/profile_spec.rb:23:in `block (2 levels) in <top (required)>'
3) Profile
Failure/Error: before { #profile = user.profile.build(given_name: "Michael", surname: "Colin") }
NoMethodError:
undefined method `build' for nil:NilClass
# ./spec/models/profile_spec.rb:23:in `block (2 levels) in <top (required)>'
4) Profile
Failure/Error: before { #profile = user.profile.build(given_name: "Michael", surname: "Colin") }
NoMethodError:
undefined method `build' for nil:NilClass
# ./spec/models/profile_spec.rb:23:in `block (2 levels) in <top (required)>'
5) Profile
Failure/Error: before { #profile = user.profile.build(given_name: "Michael", surname: "Colin") }
NoMethodError:
undefined method `build' for nil:NilClass
# ./spec/models/profile_spec.rb:23:in `block (2 levels) in <top (required)>'
6) Profile user
Failure/Error: before { #profile = user.profile.build(given_name: "Michael", surname: "Colin") }
NoMethodError:
undefined method `build' for nil:NilClass
# ./spec/models/profile_spec.rb:23:in `block (2 levels) in <top (required)>'
7) Profile when user_id is not present
Failure/Error: before { #profile = user.profile.build(given_name: "Michael", surname: "Colin") }
NoMethodError:
undefined method `build' for nil:NilClass
# ./spec/models/profile_spec.rb:23:in `block (2 levels) in <top (required)>'
8) Profile accessible attributes should not allow access to user_id
Failure/Error: before { #profile = user.profile.build(given_name: "Michael", surname: "Colin") }
NoMethodError:
undefined method `build' for nil:NilClass
# ./spec/models/profile_spec.rb:23:in `block (2 levels) in <top (required)>'
Finished in 1.56 seconds
29 examples, 8 failures
Failed examples:
rspec ./spec/models/profile_spec.rb:27 # Profile
rspec ./spec/models/profile_spec.rb:28 # Profile
rspec ./spec/models/profile_spec.rb:29 # Profile
rspec ./spec/models/profile_spec.rb:30 # Profile
rspec ./spec/models/profile_spec.rb:33 # Profile
rspec ./spec/models/profile_spec.rb:31 # Profile user
rspec ./spec/models/profile_spec.rb:37 # Profile when user_id is not present
rspec ./spec/models/profile_spec.rb:41 # Profile accessible attributes should not allow access to user_id
Done.
>
.
require 'spec_helper'
describe Profile do
# before do
# This code is wrong but it works
# #profile = Profile.new(given_name: "Michael", surname: "Colin", user_id: user.id)
# end
# but I am attempting to create a profile via User/Profile assoications
let(:user) { FactoryGirl.create(:user) }
before { #profile = user.profile.build(given_name: "Michael", surname: "Colin") }
subject { #profile }
it { should respond_to(:given_name) }
it { should respond_to(:surname) }
it { should respond_to(:user_id) }
it { should respond_to(:user) }
its(:user) { should == user }
it { should be_valid }
describe "when user_id is not present" do
before { #profile.user_id = nil }
it { should_not be_valid }
end
describe "accessible attributes" do
it "should not allow access to user_id" do
expect do
Profile.new(user_id: user_id)
end.should raise_error(ActiveModel::MassAssignmentSecurity::Error)
end
end
end

Answer 1

has_one will give you a build_profile method on user. See http://guides.rubyonrails.org/association_basics.html#has_one-association-reference for more details.
The reason you can't do user.profile.build is that there is no profile, so user.build returns nil and it doesn't make sense to ask nil to build a profile. This is different to the has_many case, where out always returns a collection of things - even when the collection is empty - and you can ask the collection to make another member. It's easy to imagine the has_one accessor returning a non-nil "I'm not here" value, which would enable your scenario, but would have other issues (mainly that such a value would not be falsey, leading to arguably less rubyesque code)