CODEWITHSUNDEEP
ruby-on-railsactiverecordhas-many-through
Jonathan Evans
Jonathan Evans

Reputation: 1034

Users and Roles for a Post in Ruby on Rails

I have a number of users who have different roles in relation to a numbers of posts. These roles are owner, editor, viewer, none. Each user may only have one role for a post. I have represented this as a has many through relationship in rails as follows:

class User < ActiveRecord::Base
  has_many :roles
  has_many :posts, :through => :roles
end

class Post < ActiveRecord::Base
  has_many :roles
  has_many :users, through => :roles
end

class Role < ActiveRecord::Base
  attr_accessor :role
  belongs_to :users
  belongs_to :posts
end

Where the role attribute is used to indicate which type of role the user has on the post. When setting a new role I cannot simply use the << operator as it wont set the role attribute. What is the preferred way of handling this situation? How can I enforce that there is only one role per user / post combination and enforce this in my Role creation logic?

Upvotes: 1

Views: 119

Answers (2)

Khaled
Khaled

Reputation: 2091

I understand that you want to make sure that no user will have more than one role for a certain post. If this is what you want to achieve then you just need to add uniquness validation to your Role mode

validates :user_id, uniqueness: {scope: :post_id, message: 'User can have one role per post'}

this will ensure that the combination of user_id and post_id will be unique, you can see more on rails guide on validation with scope.

Upvotes: 0

Nishant
Nishant

Reputation: 3005

You can check in the creation of roles for the User , if he already has a role assigned in which case you can skip assigning this role.

unless user.roles.present?
  user.roles.create
end

Upvotes: 1

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