Rails3，has_many:through and:polymorphil-我应该这样做吗

Question

好的，开始吧。我不知道我是不是把事情复杂化了，还是我对Rails还很陌生，以至于不了解基本知识。我想要的sudo代码是这样的：

User
has_many projects as owner through relationship
has_many projects as contributor through relationship
has_many projects as follower through relationship
Project
has_one user as owner through relationship
has_many users as followers through relationship
has_many users as contributors through relationship
Relationship
belongs_to user
belongs_to project

然后我想拥有以下神奇的东西：

owner = Project.owner
followers = Project.followers
contributors = Project.contributors
projects = User.projects
myprojects = User.projects... (now I'm really not sure)
followedProjects = ...
contributingProjects = ...

所以在写下来的时候，我可以看到我对这个模型的理解还有另一个差距。用户可以扮演所有者、追随者或贡献者的角色，也可以是这三者的任意组合。

就实际代码而言，我在这里添加了我认为相关的部分：

class User < ActiveRecord::Base
  has_many :user_project_relationships, :as => :relateable, :class_name => "UserProjectRelationship"
  has_many :projects, :as => :owner, :through => :relateable, :class_name => "Project", :source_type => :owner
  has_many :projects, :as => :follower, :through => :relateable, :class_name => "Project", :source_type => :follower
  has_many :projects, :as => :contributor, :through => :relateable, :class_name => "Project", :source_type => :contributor
end
class Project < ActiveRecord::Base
  has_many :user_project_relationships, :as => :relateable, :class_name => "UserProjectRelationship"
  has_one :user, :as => :owner, :through => :relateable, :class_name => "User"
  has_many :users, :as => :followers, :through => :relateable, :source_type => :follower, :class_name => "User"
  has_many :users, :as => :contributors, :through => :relateable, :source_type => :contributor, :class_name => "User"
end
class UserProjectRelationship < ActiveRecord::Base
  belongs_to :user
  belongs_to :project, :polymorphic => true
end

关系模型的迁移是：

class CreateUserProjectRelationships < ActiveRecord::Migration
  def self.up
    create_table :user_project_relationships do |t|
      t.integer :relateable_id
      t.string :relateable_type
      t.integer :project_id
      t.timestamps
    end
    add_index :user_project_relationships, [:relateable_id, :relateable_type], :name => :relateable
    add_index :user_project_relationships, :project_id
  end
  def self.down
    drop_table :user_project_relationships
  end
end

目前，我在project.users ActiveRecord::HasManyThroughAssociationNotFoundError: Could not find the association :relateable in model Project 等方面遇到错误

我觉得我在这里太荒无人烟了，无法真正得到我想要的，也许依靠神奇的栏杆可以做得更多。任何关于最佳路径的指导都将不胜感激。

提前感谢

Steve

Answer 1

Rails可以做很多事情，但我认为您试图让Relationship模型做得太多了。每一种关系都是不同的，所以我想尽量保持这种关系

将其拆分为单独的连接模型：

class User < ActiveRecord::Base
  has_many :owned_projects, :class_name => "Project", :foreign_key => :owner_id
  has_many :projects_followers
  has_many :followed_projects, :class_name => "Project", :through => :projects_followers
  has_many :projects_contributors
  has_many :contributed_projects, :class_name => "Project", :through => :projects_contributors
end
class Project < ActiveRecord::Base
  belongs_to :owner
  has_many :projects_followers
  has_many :followers, :class_name => "User", :through => :projects_followers

  has_many :projects_contributors, :foreign_key => :contributor_id
  has_many :contributors, :class_name => "User", :through => :projects_contributors
end
class ProjectsFollowers < ActiveRecord::Base
  belongs_to :user
  belongs_to :project
end
class ProjectsContributors < ActiveRecord::Base
  belongs_to :user
  belongs_to :project
end

应该更接近你想要的。然后你确实可以做

project.owner
project.followers
project.contributors

和

user.owned_projects
user.followed_projects
user.contributed_projects

这要么有效，要么让你非常接近。

我认为你的混乱是因为试图建立多态关系，我认为这在这里是不可取的。AFAI grok，多态关系的用例是当您希望1个模型以相同的方式与任何数量的其他模型相关时。这里的情况并非如此，因为您有两个模型，它们之间有3种不同类型的关系。