Question

My migration right now :

class CreateActivities < ActiveRecord::Migration
  def self.up
    create_table :activities do |t|
      t.integer :account_id, :null => false
      t.integer :target_id, :null => false
      t.string  :target_type, :null => false
      t.string  :event_type, :null => false
      t.integer :employee_id
      t.string  :name
      t.timestamps
    end

    add_index :activities, [:target_id, :target_type]

With this I can now call a target like so :

Activity.first.target

And it will bring up the target_id, based on the target_type.

How would I do the opposite of that so that I can select a target, and if it has any associated Activities, they will show up?

Like so :

Job.find(1234).activities
# Where Job.find(1234) is the target_id of many activities.

Answer 1

If I understand right, this should do it:

class Job < ActiveRecord::Base
  has_many :activities, :conditions => ['target_type = ?', 'Job'], :as => :target
end