How to get Collection object throug Many to Many relationship in Ruby on Rails

Friends I've following models

class Project < ActiveRecord::Base
  has_many :milestones_projects
  has_many :milestones, :through => :milestones_projects
  validates :projectname, :presence=>true, :length=> {:maximum=>250}, :uniqueness=>true
  validates :location,:presence=>true
end

class Milestone < ActiveRecord::Base
  has_many :milestones_projects
  has_many :projects, :through => :milestones_projects

  validates :name, :presence => true, :length => {:maximum => 250}
  validates :days, :presence => true, :length => {:maximum => 3}
  validates :stage, :presence => true
end


class MilestonesProjects < ActiveRecord::Base
  belongs_to :milestones,:foreign_key => 'milestone_id'
  belongs_to :projects,:foreign_key => 'project_id'
end

So i have many-to-many relationship between project and milestone.

in irb, I want to get collection object, so I'm using as following

开发者_运维百科irb(main):001:0> me=Project.find(1)
=> #<Project id: 1, location_id: 1, projectname: "Sample 2", description: "Sample 2", i
spublished: true, created_at: "2011-09-02 08:26:41", updated_at: "2011-09-07 10:26:48">

here 'me' is an array contains first project details, and now i"m trying to get milestone details associated with this project. for this I'm trying as follows

irb(main):002:0> me.milestones

but it's giving me error like

NameError: uninitialized constant Project::MilestonesProject from c:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/gems/activerecord-3.0.9/lib/ active_record/base.rb:1205:in compute_type' from c:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/gems/activerecord-3.0.9/lib/ active_record/reflection.rb:162:insend' from c:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/gems/activerecord-3.0.9/lib/ active_record/reflection.rb:162:in klass' from c:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/gems/activerecord-3.0.9/lib/ active_record/reflection.rb:346:insource_reflection' from c:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/gems/activerecord-3.0.9/lib/ active_record/reflection.rb:346:in collect' from c:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/gems/activerecord-3.0.9/lib/ active_record/reflection.rb:346:insource_reflection' from c:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/gems/activerecord-3.0.9/lib/ active_record/reflection.rb:377:in check_validity!' from c:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/gems/activerecord-3.0.9/lib/ active_record/associations/association_proxy.rb:61:ininitialize' from c:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/gems/activerecord-3.0.9/lib/ active_record/associations/association_collection.rb:23:in initialize' from c:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/gems/activerecord-3.0.9/lib/ active_record/associations/has_many_association.rb:11:ininitialize' from c:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/gems/activerecord-3.0.9/lib/ active_record/associations.rb:1483:in new' from c:/RailsInstaller/Ruby1.8.7/lib/ruby/gems/1.8/gems/activerecord-3.0.9/lib/ active_record/associations.rb:1483:inmilestones' from (irb):2 from :0

so friends please help me..

i need to execute some commands like

milestone_count=project.milestones.size

thanks for your quick response! Finally i found the solution, both the answers posted here are correct..

i changed my models like this

class Project < ActiveRecord::Base
  has_many :project_milestones
  has_many :milestones, :through => :project_milestones
end

class Milestone < ActiveRecord::Base  
  has_many :project_milestones
  has_many :projects, :through => :project_milestones
end

class ProjectMilestone < ActiveRecord::Base
  belongs_to :milestone,:foreign_key => 'milestone_id'
  belongs_to :project,:foreign_key => 'project_id'
end

I suspect that the naming conventions of rails are here the problem. Rails thinks that your model objects are singular, and your data base tables are plural. Rails could have a problem with a model named MilestonesProjects, it should be named MilestoneProject because that is it: the relation between one Milestone and one Project. Have a look at the example in "Guide to Active Records", section 2.4 and where singular and plural is used.

try this code in your MilestonesProjects model

class MilestonesProjects < ActiveRecord::Base
  belongs_to :milestone,:foreign_key => 'milestone_id'
  belongs_to :project,:foreign_key => 'project_id'
end