Relationships in Ruby on Rails across 4 models

Question

I am trying to make some advanced relationships in my RoR models.

S far what I have working is projects and tasks- Projects have tasks and users have projects.

I now want that a user who is 'signed up' to a project can now 'sign up' to tasks within that project.

My current classes in brief:

class AdminUser < ActiveRecord::Base
 has_and_belongs_to_many :projects
 has_and_belongs_to_many  :tasks
 has_many :admin_users_projects

[...]


class AdminUsersProject < ActiveRecord::Base

  belongs_to :admin_user
  has_and_belongs_to_many :project
  has_many :tasks

[...]

class Project < ActiveRecord::Base

  has_many :tasks
  has_and_belongs_to_many :admin_users
  has_and_belongs_to_many :admin_users_projects

[...]

class Task < ActiveRecord::Base

  belongs_to :project
  has_and_belongs_to_many :admin_users
  belongs_to :admin_users_project

[...]

The Schema looks like this:

 create_table "admin_users", :force => true do |t|
    t.string   "first_name",      :limit => 25
    t.string   "last_name",       :limit => 50
    t.string   "email",           :limit => 100, :default => "", :null => false
    t.string   "hashed_password", :limit => 40
    t.datetime "created_at",                                     :null => false
    t.datetime "updated_at",                                     :null => false
    t.string   "username",        :limit => 25
    t.string   "salt",            :limit => 40
  end

  add_index "admin_users", ["username"], :name => "index_admin_users_on_username"

  create_table "admin_users_projects", :force => true do |t|
    t.integer "admin_user_id"
    t.integer "project_id"
  end

  add_index "admin_users_projects", ["admin_user_id", "project_id"], :name =>     "index_admin_users_projects_on_admin_user_id_and_project_id"

  create_table "projects", :force => true do |t|
    t.string   "name"
    t.integer  "position"
    t.boolean  "visible",    :default => false
    t.datetime "created_at",                    :null => false
    t.datetime "updated_at",                    :null => false
  end

  create_table "tasks", :force => true do |t|
    t.integer  "project_id"
    t.string   "permalink"
    t.integer  "position"
    t.boolean  "visible"
    t.datetime "created_at",    :null => false
    t.datetime "updated_at",    :null => false
    t.string   "name"
    t.integer  "admin_user_id"
    t.integer  "progress"
  end

  add_index "tasks", ["permalink"], :name => "index_tasks_on_permalink"
  add_index "tasks", ["project_id"], :name => "index_tasks_on_project_id"

end

I have view that show projects and then a view of their subset of tasks I also have a view that shows a users projects but now I want it to show that users subset of tasks.

My view for 'admin_user_projects' in brief is as follows:

    <% @admin_users_projects.each do |admin_users_projects| %>
    <tr>
        <td><%= admin_users_projects.admin_user_id %></td>
        <td><%= admin_users_projects.admin_user.username  %></td>
        <td><%= admin_users_projects.project_id %></td>
        <td><%= admin_users_projects.project.name  %></td>
    </tr>
    <% end %>

This shows the users id, username, project id and project name. I now want to add a row showing how many tasks a user is 'signed up' to for that project. I have tried

        <td><%= admin_users_projects.tasks.size  %></td>

But get the following:

Mysql2::Error: Unknown column 'tasks.admin_users_project_id' in 'where clause': SELECT COUNT(*) FROM `tasks`  WHERE `tasks`.`admin_users_project_id` = 1

Does anyone have any ideas how to get these relationships working effectively?

Answer 1

My suggestion is this:

class AdminUser < ActiveRecord::Base
  has_and_belongs_to_many :projects
  has_many :assigned_tasks
  has_many :tasks, through: :assigned_tasks
end

class AssignedTask < ActiveRecord::Base
  belongs_to :user
  belongs_to :task

  validate :user_assigned_to_project

  private

  def user_assigned_to_project
    unless user.projects.include? task.project
      errors.add(:project, "is not valid")
    end
  end
end

class Project < ActiveRecord::Base
  has_and_belongs_to_many :admin_users
  has_many :tasks
end

class Task < ActiveRecord::Base
  has_many :assigned_tasks
  has_many :users, through: :assigned_tasks
  belongs_to :project
end


class GiantMigration < ActiveRecord::Migration
  create_table :admin_users do |t|
    # whatever
  end
  create_table :projects do |t|
    # whatever
  end
  create_table :assigned_tasks do |t|
    t.integer :admin_user_id, null: false
    t.integer :task_id, null: false
  end
  create_table :tasks do |t|
    # whatever
    t.integer :project_id
  end
  create_table :admin_users_projects, id: false do |t|
    t.integer :admin_user_id, null: false
    t.integer :project_id, null: false
  end
end

Some general notes:

• You have to choose if you're going to use pure join table (HABTM) or a join model (has_many :through). Right now you're mixing the two.
• Don't use force: true in your migrations as default.
• Stick to Rails' conventions: has_and_belongs_to_many :projects (you used project, in singular)

Answer 2

You don't have a relationship

class AdminUsersProject < ActiveRecord::Base
  has_many :tasks

unless the tasks table has a foreign key with the name admin_users_project_id.

I suspect that you don't have many tasks for an AdminUsersProjects linking record.

Instead I think you want the admin user's tasks, or the project's tasks.

Until you clarify what you want, no one can help you. Once you are clear about what you want, you may be able to figure out the answer yourself.