How to add a new entry to a multiple has_many association?

Question

I am not sure am I doing these correct.

I have 3 models, Account, User, and Event.

Account contains a group of Users. Each User have its own username and password for login, but they can access the same Account data under the same Account.

Events is create by a User, which other Users in the same Account can also read or edit it.

I created the following migrations and models.

---

User migration

class CreateUsers < ActiveRecord::Migration
  def self.up
    create_table :users do |t|
      t.integer     :account_id
      t.string      :username
      t.string      :password
      t.timestamps
    end
  end

  def self.down
    drop_table :users
  end
end

---

Account migration

class CreateAccounts < ActiveRecord::Migration
  def self.up
    create_table :accounts do |t|
      t.string      :name
      t.timestamps
    end
  end

  def self.down
    drop_table :accounts
  end
end

---

Event migration

class CreateEvents < ActiveRecord::Migration
  def self.up
    create_table :events do |t|
      t.integer     :account_id
      t.integer     :user_id
      t.string      :name
      t.string      :location
      t.timestamps
    end
  end

  def self.down
    drop_table :events
  end
end

---

Account model

class Account < ActiveRecord::Base
  has_many      :users
  has_many      :events
end

---

User model

class User < ActiveRecord::Base
  belongs_to    :account
end

---

Event model

class Event < ActiveRecord::Base
  belongs_to    :account
  belongs_to    :user
end

---

so....

1. Is this setting correct?
2. Every time when a user create a new account, the system will ask for the user information, e.g. username and password. How can I add them into correct tables?
3. How can I add a new event?

I am sorry for such a long question. I am not very understand the rails way in handling such data structure. Thank you guys for answering me. :)

Answer 1

This looks like a job for has_many :through (scroll down to find the :through option)

If you need to know the user that created the event, then you should specify that Event really belongs only to a user:

class Event < ActiveRecord::Base
  belongs_to    :user
end

Accounts, however, can "grab" their user's events. You specify that like this:

class User < ActiveRecord::Base
  belongs_to :account
end

class Account < ActiveRecord::Base
  has_many :users
  has_many :events, :through => :users
end

The migrations would be the same as you wrote for Account and User. For Event you can remove the account_id:

class CreateEvents < ActiveRecord::Migration
  def self.up
    create_table :events do |t|
      t.integer     :user_id
      t.string      :name
      t.string      :location
      t.timestamps
    end
  end

  def self.down
    drop_table :events
  end
end

Then your events can be created like this:

# These two are equivalent:
event = user.events.create(:name => 'foo', :location => 'bar')
event = Event.create(:user_id => user.id, :name => 'foo', :location => 'bar')

Notice that this will create and save the event inmediately. If you want to create the event without saving it, you can use user.events.build or Event.new instead.

The has_many :through on Accounts will allow you to get all the events for one account:

user.events         # returns the events created by one user
account.events      # returns all the events created by the users of one account
user.account.events # returns the events for the user's account

As a final note, please note that you are reinventing the wheel a lot here. There are pretty good solutions out there for managing users and permissions.

I recommend you to have a look at devise (railscast) or authlogic (railscast) for managing your accounts, and declarative_authorization(railscast) or cancan(railscast) for managing permissions. My personal choices are devise and declarative_authorization. The former is easier to install than authlogic, and the later is more powerful than cancan.

Regards, and good luck!