Rails nested form on HABTM: how to prevent duplicate entry? - ruby-on-rails-3

Question

I have simple app with 3 tables in DB and 'many-to-many' relationships.
# Model Employee
class Employee < ActiveRecord::Base
has_and_belongs_to_many :phonenumbers
accepts_nested_attributes_for :phonenumbers, :allow_destroy => true
attr_accessible :last_name, :first_name, :middle_name, :phonenumbers_attributes
end
# Model Phonenumber
class Phonenumber < ActiveRecord::Base
has_and_belongs_to_many :employees
attr_accessible :number
accepts_nested_attributes_for :employees
end
I have 'employees_phonenumbers' join-table with 'employee_id' and 'phonenumber_id' columns.
# View
<%= form_for #employee, :url => { :action => :create } do |f| %>
<%= f.label "Last name" %>
<%= f.text_field :last_name %>
<%= f.label "First name" %>
<%= f.text_field :first_name %>
<%= f.label "Middle name" %>
<%= f.text_field :middle_name %>
<%= f.fields_for :phonenumbers do |phonenumber| %>
<%= phonenumber.label "Phone number" %>
<%= phonenumber.telephone_field :number %>
<% end %>
<%= f.submit "Create" %>
<% end %>
# Controller
def create
#employee = Employee.new(params[:employee])
#employee.save ? (redirect_to :action => :index) : (render "new")
end
Now if I create a user: 'John' with phone number '555', it's OK.
But if I want to create a user 'Larry' with the same phone number '555', there's a dublicate of '555' entry in the DB.
How do I prevent this?
UPDATE: My logic is: If there is number '555', then do not create a new one, use existing. If there is no such a number, then create a new one and use it.

Answer 1

in employee.rb:
before_save :get_phonenumbers
def get_phonenumbers
self.phonenumbers = self.phonenumbers.collect do |phonenumber|
Phonenumber.find_or_create_by_number(phonenumber.number)
end
end
I have found its working

Answer 2

You can use rails validation to check uniqueness of record.
In your model phonenumber.rb put following line,
validates_uniqueness_of :column_name
It will ensure that Phonenumber will have unique phone_numbers only.
Now in controller you can check phone_number from params and if number is already exist then we will delete nested attributes fron params so that Phonenumber record wont generate.
def create
#phone_number = Phonenumber.where(:number=>params[:employee][:phonenumber][:number])
if #phone_number.any?
params[:employee].delete(:phonenumber)
#employee = Employee.new(params[:employee])
if #employee.save?
#employee.phonenumber = #phone_number.first
redirect_to :action => :index
else
render "new"
end
else
#employee = Employee.new(params[:employee])
#employee.save ? (redirect_to :action => :index) : (render "new")
end
end