造型相同的模型之间两种不同的关系 [英] Modelling two different relationships between the same models

问题描述

两种模式组织和用户有一个1：一对多的关系，其中一个组织有多个用户（会员;用户还可以的不的关联，以任何组织）：

Two models Organization and User have a 1:many relationship, where an organization has multiple users (members; a user can also not be associated to any organization):

class Organization < ActiveRecord::Base
  has_many :users, dependent: :destroy
  accepts_nested_attributes_for :users, :reject_if => :all_blank, :allow_destroy => true
  validates_associated :users
end

class User < ActiveRecord::Base
  belongs_to :organization, inverse_of: :users
end

一切正常，测试各种通过。结果
现在，我增加了一个功能的主持人，用户可以有（多）组织版主权限的附加关系。因此，一个不少：通过第三模型，我命名为主持人一对多的关系：

Everything worked, all sorts of tests pass.
Now I added an additional relationship for a moderator function, where users can have moderator rights for (multiple) organizations. Hence, a many:many relationship through a third model, which I named Moderator:

class Organization < ActiveRecord::Base
  has_many :users, dependent: :destroy
  accepts_nested_attributes_for :users, :reject_if => :all_blank, :allow_destroy => true
  has_many :moderators, class_name: "Moderator", foreign_key: "reviewee_id", dependent: :destroy
  has_many :users, through: :moderators, source: :reviewer
  validates_associated :users
end

class User < ActiveRecord::Base
  belongs_to :organization, inverse_of: :users
  has_many :moderators, class_name:  "Moderator",   foreign_key: "reviewer_id", dependent: :destroy
  has_many :organizations, through: :moderators, source: :reviewee
end

class Moderator < ActiveRecord::Base
  belongs_to :reviewee, class_name: "Organization"
  belongs_to :reviewer, class_name: "User"
end

我故意使用了审核和 reviewee 名称。如果我只是在主持人模型中使用 USER_ID 和 organization_id ，我虽然这可能会误事。因为如果你再参考 @ user.organization 那就不是被定义为使用的关系。难道使用1：用户和组织，或者很多很多之间的关系：通过很多关系......？通过使用不同的名称很多：通过关系很多， @ user.organization 应该指的是1：一对多的关系，而 @ user.reviewee 例如应该是指很多：很多关系，通过

I intentionally used the reviewer and reviewee names. If I would just use user_id and organization_id in the Moderator model, I though this could mess things up. Because if you would then refer to @user.organization then it wouldn't be defined which relationship to use. Would it use the 1:many relationship between user and organization, or the many:many through relationship...? By using different names for the many:many through relationship, @user.organization should refer to the 1:many relationship, while @user.reviewee for example should refer to the many:many through relationship.

不过，这个实施后，顿时测试各种失败。例如：我有签约额外的用户为一个组织的形式。 Clicing按钮传递organization_id于为其附加的用户是要创建的形式。现在突然这个id没有传递的形式和我得到的所有无错误，因为该组织没有被定义（即使链接依然如 URL /会员？organization_id = 43 ）。而我可以为更多的例子。

Nevertheless, after this implementation, suddenly all sorts of tests fail. For example: I have a form that signs up an additional user for an organization. Clicing a button passes the organization_id to the form for which an additional user is to be created. Now suddenly this id doesn't get passed on to the form and I get all nil error because the organization isn't defined (even though the link still is e.g. url/member?organization_id=43). And I could give many more examples.

所以，似乎有某种冲突，因为新的关系。也许是不明白何时使用多比多通过关系，当1：一对多的关系，即使我用differend评审和reviewee名称... 有我模仿它不正确或已不可能有两个同一型号的2之间的不同关系？的

So there seems to be some kind of conflict because of the new relationship. Perhaps it fails to understand when to use the many:many through relationship and when the 1:many relationship, even though I used the differend reviewer and reviewee names... Have I modelled it incorrectly or is it impossible to have two different relationships between 2 of the same models?

如果我删除第二个的has_many：用户从组织模型的所有测试再次通过线。所以，问题似乎是，我有这个关系的两倍。

If I remove the second has_many :users line from the Organization model all tests pass again. So the problem seems to be that I have this relationship twice.

推荐答案

有关处理一个很好的和共同的模式被称为资源的局部角色。

A good and common pattern for dealing with this is called resource scoped roles.

一个用户可以在某些案件中的作用范围限于特定的资源很多角色（父亲，母亲，主持人，草裙舞舞者等）。像父/母的作用范围是用户（孩子）或主持人可以作用域到论坛。

A User can have many roles (father, mother, moderator, hula-dancer etc) in some cases the Role is scoped to a particular resource. Like father/mother is scoped to a User (the child) or a moderator can be scoped to a Forum.

拥有一个像系统级的角色而不是作用域资源超级管理员也很常见。

class User < ActiveRecord::Base
  has_many :roles
  scope :moderators, ->{ joins(:roles).where( roles: { name: 'moderator' } ) }
  belongs_to :organization
end

# columns: name:string, resource_id:int, resource_type:string, user_id:int
class Role < ActiveRecord::Base
  belongs_to :user
  belongs_to :resource, polymorphic: true
end

class Organization < ActiveRecord::Base
  has_many :roles, as: :resource
  has_many :users
  # This is just a relationship to users with a scope
  has_many :moderators, -> { moderators }, class_name: 'User'
end

所以要加一个主持人，我们会做：

So to add a moderator we would do:

organization = Organization.find(1)
organization.roles.create(user: organization.users.find(1), name: 'moderator')

要获得所有版主的组织：

To get all moderators for a organization:

moderators = Organization.find(1).moderators

在这里真棒事情是，我们可以用我们的角色类的任何资源 - 不只是一个组织。更妙的是，有很大的宝石来提供这种功能，如 Rolify 。

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