Optional many to many relationship in rails?

问题

Is there a way to produce an optional many to many relationship in rails?

I have a Client model and a ClientManager model - And I want a Client to have 0, 1 or many client_managers. But I'd also like a Clientmanger to be able to have 0, 1 or more clients. Is this possible? And how?

Using rails 5.

Updated for clarity/purpose: I want clientmanagers, to be able to manage multiple clients, or even none. And clients to be able to be managed by 0, 1 or multiple client-managers

回答1:

If it's an NxN relationship, you should create another model that belongs to both Client and ClientManager. Let's call it Management, for instance:

rails g model Management client:references client_manager:references

That would generate something like this:

class Management < ActiveRecord::Base
  belongs_to :client
  belongs_to :client_managers
end

and then, on your Client model:

  has_many :managements
  has_many :client_managers :through => :managements

and on your ClientManager:

  has_many :managements
  has_many :clients :through => :managements

Hope this helps you figure out. Good Luck!

回答2:

You can also use has_and_belongs_to_many association.

Your models would be

class Client < ActiveRecord::Base
  has_and_belongs_to_many :managers
end

class Manager< ActiveRecord::Base
  has_and_belongs_to_many :clients
end

回答3:

this is a straightforward many-to-many relationship with has_many through relation between Client and ClientManager data models. For this, you need to setup 3 tables in your db clients, client_managers, projects

# models/client.rb
class Client < ApplicationRecord
  has_many :projects
  has_many :client_managers, through: :projects
end

# models/project.rb
# projects table schema should have- client_id:integer client_manager_id:integer
class Project < ApplicationRecord
  belongs_to :client
  belongs_to :client_manager
end    

# models/client_manager.rb
class ClientManager < ApplicationRecord
  has_many :projects
  has_many :clients, through: :projects
end

Access

Client.last.client_managers gives 0, 1 or many client_managers associated with Client.last

ClientManager.last.clients gives 0, 1 or many clients associated with ClientManager.last

more info here

来源：https://stackoverflow.com/questions/40888515/optional-many-to-many-relationship-in-rails

标签

ruby-on-rails

ruby-on-rails-5