Rails多對多：通過類屬性合併？

Question

我有以下的許多一對多的關係：

class Assignment < ActiveRecord::Base 
    belongs_to :programmer 
    belongs_to :project 
end 

class Programmer < ActiveRecord::Base 
    has_many :assignments 
    has_many :projects, :through => :assignments 
end 

class Project < ActiveRecord::Base 
    has_many :assignments 
    has_many :programmers, :through => :assignments 
end 

在我的分貝：遷移我有以下幾點：

class CreateAssignments < ActiveRecord::Migration 
    def self.up 
    create_table :assignments do |t| 
     t.integer :programmer_id 
     t.integer :project_id 
     t.boolean :owner, :default => false 
     t.timestamps 
    end 
    end 

def self.down 
    drop_table :assignments 
end 
end 

這意味着我可以加載屬於程序員項目，這樣做：

@my_programmer.projects.find params[:id] 

但是，如果你看到我的遷移，每個分配也有一個「所有者」標誌，表示程序員是否是的主人項目。我的問題是這個查詢只會給我這個項目，而不能訪問「所有者」標誌。

那麼如何知道程序員是否是所有者呢？我可以通過另一個電話來獲得協作，但它似乎很愚蠢，因爲它已經在分配上進行JOIN了？

有沒有辦法獲得：through類的屬性，而無需執行特定的數據庫調用？

Answer 1

這是相當奇怪的數據庫體系結構。不過你可以試試這個

class Programmer < ActiveRecord::Base 
    has_many :assignments 
    has_many :projects, :through => :assignments 

    def own_projects 
    projects.where(:owner => true) 
    end 
end 

class Project < ActiveRecord::Base 
    has_many :assignments 
    has_many :programmers, :through => :assignments 

    def owners 
    programmers.where(:owner => true) 
    end 

    def collaborators 
    programmers.where(:owner => false) 
    end 
end 

@my_programmer.own_projects 
@my_project.owners 
@my_project.owners.include? @my_programmer 
@my_project.colaborators 

UPD

另一種解決方案，使用預先加載：

class Programmer < ActiveRecord::Base 
    has_many :assignments 
    has_many :projects, :through => :assignments 
    has_many :own_projects, :class_name => "Project", :through => :assignments, :conditions => ['assignments.owner = ?', true], :source => :project 
end 

class Project < ActiveRecord::Base 
    has_many :assignments 
    has_many :programmers, :through => :assignments 
    has_many :owners, :class_name => "Programmer", :through => :assignments, :conditions => ['assignments.owner = ?', true], :source => :programmer 
    has_many :collaborators, :class_name => "Programmer", :through => :assignments, :conditions => ['assignments.owner = ?', false], :source => :programmer 
end 

@my_programmer.projects.includes(:owners).each do |project| 
    project.owner 
end