Rails idiom to avoid duplicates in has_many :through

Question

I have a standard many-to-many relationship between users and roles in my Rails app:

class User < ActiveRecord::Base
  has_many :user_roles
  has_many :ro         


        

Answer 1

Use Array's |= Join Method.

You can use Array's |= join method to add an element to the Array, unless it is already present. Just make sure you wrap the element in an Array.

role                  #=> #

user.roles            #=> []

user.roles |= [role]  #=> [#]

user.roles |= [role]  #=> [#]

Can also be used for adding multiple elements that may or may not already be present:

role1                         #=> #
role2                         #=> #

user.roles                    #=> [#]

user.roles |= [role1, role2]  #=> [#, #]

user.roles |= [role1, role2]  #=> [#, #]

Found this technique on this StackOverflow answer.