Question

Lets say I want to create a database of finished coding projects, developers, and their roles.

The models look like this:

project has_and_belongs_to_many developers
developers has_and_belongs_to_many projects

The developers_projects table look like this:

int: developer_id, project_id
string: role

Lets day I have 3 Developers and 2 projects with their respective id and names as

1, Ashley
2, Bob
3, Charles

1, Tic Tac Toe
2, Snake

And their actual roles being

Project 1:
- Manager: Ashley
- Coder: Bob, Charles

Project 2:
- Manager: Charles
- Coder: Ashley

Is it possible to define a managers and coders object under projects?

like:

class Project < ActiveRecord::Base
    has_and_belongs_to_many :developers
    has_and_belongs_to_many :managers, :class_name => "developers", :condition => "role = 'manager'"
    has_and_belongs_to_many :coders, :class_name => "developers", :condition => "role = 'coder'"
end

(this does not work)

Thank you in advance,

Answer 1

has_and_belongs_to_many allows to create join tables without declaring model. As far as you want to have attribute in this table you should create separate model, for example, ProjectRoles in your case:

class ProjectRole < ActiveRecord::Base
  belongs_to :developer
  belongs_to :project

  attr_accessible :role
end

class Project < ActiveRecord::Base
  has_many :manager_roles, :class_name => "ProjectRole", 
                           :conditions => { :role => 'manager' }
  has_many :managers, :through => manager_roles
end

class Developer < ActiveRecord::Base
  has_many :project_roles
  has_many :projects, :through => project_roles
end