How to setup a one to many relationship?

问题

I have the following models:

User (id, name, network_id)
Network(id, title)

What kind of Rails model assoc do I need to add so that I can do:

@user.network.title
@network.users

Thanks

回答1:

so network has_many users and a user belongs_to network.

Just add a network_id to users table if you still haven't and also since it's a foreign_key is worth indexing it.

rails generate migration AddNetworkIdToUsers

class AddNetworkIdToUsers < ActiveRecord::Migration
  def change
    add_column :users, :network_id, :integer
    add_index  :users, :network_id
  end
end

In the network model do:

class Network < ActiveRecord::Base
  has_many :users
end

In the user model do:

class User < ActiveRecord::Base
  belongs_to :network
end

回答2:

According to your database-setup, you just have to add the following lines to your models:

class User < ActiveRecord::Base
  belongs_to :network
  # Rest of your code here
end

class Network < ActiveRecord::Base
  has_many :users
  # Rest of your code here
end

In case you have a setup without network_id, you should go with daniels answer.

回答3:

This is my way: run:

$rails generate migration AddNetworkIdToUsers

then config migration file:

class AddNetworkIdToUsers < ActiveRecord::Migration[5.1]

  def up

    add_column :users, :network_id, :integer
    add_index  :users, :network_id
  end

  def down

    remove_index :users, :network_id
    remove_column :users, :network_id
  end

end

来源：https://stackoverflow.com/questions/8555082/how-to-setup-a-one-to-many-relationship