Rails 3跨多个模型自动完成

class User< ActiveRecord::Base
  has_many :user_projects
  has_many :projects, through: :user_projects
end

class Project< ActiveRecord::Base
  has_many :user_projects
  has_many :users, through: :user_projects
end

class UserProject< ActiveRecord::Base
  belongs_to :user
  belongs_to :project
end

class UserProject< ActiveRecord::Base
  belongs_to :user
  belongs_to :project

  validates :complete, inclusion: { in: [true, false] }
end

class User< ActiveRecord::Base
  has_many :user_projects
  has_many :projects, through: :user_projects

  def complete_project(project)
    user_project = user_projects.find_by(project: project)
    user_project.update(complete: true)
  end
end

class Project< ActiveRecord::Base
  has_many :user_projects
  has_many :users, through: :user_projects

  def complete_user(user)
    user_project = user_projects.find_by(user: user)
    user_project.update(complete: true)
  end
end