Question

目前我已经建立了数据库模型并可以使用数据填充模型：

   user.persons << person
    group.functions << function
    group.classificationlevels << clasfication
    user.groups << group

这些是我目前使用的模型，用于获取彼此相关的数据：

module Core_authentication

  class User
    include DataMapper::Resource

    property :id, Serial
    property :username, String, :required => true, :unique => true  
    property :password, BCryptHash, :required => true 
    property :email, String, :format => :email_address, :required => true
    property :created_at, DateTime
    property :updated_at, DateTime

    #Creating join tables to link to group and person information
    has n, :persons, :through => Resource
    has n, :groups, :through => Resource

    def username= new_username
      super new_username.downcase
    end

  end 

  class Group
    include DataMapper::Resource

    property :id, Serial
    property :groupname, String, :required => true

    #Another jointable link group to link to functions and classification levels
    has n, :functions, :through => Resource
    has n, :classificationlevels, :through => Resource
    has n, :users, :through => Resource

    def groupname= new_group
      super new_group.downcase.capitalize!
    end
  end  

  class Person
    include DataMapper::Resource

    property :id, Serial
    property :firstname, String
    property :lastname, String, :required => true
    property :adress, String
    property :postcode, String, :length => 6, :required => true
    property :telefoon, String
    property :created_at, DateTime
    property :updated_at, DateTime

    has n, :users, :through => Resource

    def firstname= new_firstname
      super new_firstname.downcase.capitalize!
    end

    def lastname= new_lastname
      super new_lastname
    end

  end  

  class Function
    include DataMapper::Resource

    property :id, Serial
    property :name, String

    has n, :groups, :through => Resource

  end  

  class Classificationlevel
    include DataMapper::Resource

    property :id, Serial
    property :levelcode, Integer
    property :name, String

    has n, :groups, :through => Resource

  end

end

我希望获得他们所属的用户组以及与每个组相关联的分类级别。

我尝试了多种方法，并在网上浏览过，但我无法找到关于如何做到这一点的明确解释，所以我无法让它发挥作用。

Answer 1

documentation for Datamapper（“有，并且属于，许多（或多对多）”部分）有一些提示，这里是模型的简化示例：

require 'sqlite3'
require 'dm-core'
require 'dm-sqlite-adapter'
require 'dm-migrations'

DataMapper.setup(:default, 'sqlite3:m2m.sqlite3')

class User
  include DataMapper::Resource
  property :id, Serial
  has n, :persons, :through => Resource # => PersonUser
  has n, :groups, :through => Resource # => GroupPerson
end

class Group
  include DataMapper::Resource
  property :id, Serial
  has n, :functions, :through => Resource # => FunctionGroup
  has n, :classificationlevels, :through => Resource # => GroupClassificationlevel
  has n, :users, :through => Resource # => GroupUser
end

class Person
  include DataMapper::Resource
  property :id, Serial
  has n, :users, :through => Resource # => PersonUser
end

class Function
  include DataMapper::Resource
  property :id, Serial
  has n, :groups, :through => Resource # => FunctionGroup
end

class Classificationlevel
  include DataMapper::Resource
  property :id, Serial
  has n, :groups, :through => Resource # => GroupClassificationlevel
end

使用它们的示例（如果您将这两个片段放在一个文件中并运行它们，您可以看到输出）：

DataMapper.finalize

DataMapper.auto_migrate!

user  = User.create
group = Group.create

# link them by adding to the relationship
user.groups << group
user.save

p user.groups # => [#<Group @id=1>]

DataMapper多对多关联

1 个答案: