幫助Rails ActiveRecord管理查詢

Question

我有3個模型。 Users，Groups,Employees所有這三個都有很多。

• 用戶有很多組
• 組有許多用戶
• 羣體有多少員工
• 員工有許多團體

所以，我創建了兩個新型號：

• Departments（在之間處理多對多和Groups）
• Employments（處理多對多Groups和 Employees之間）

我相信我有這個正確的紙張上，但我不能讓它下來代碼正確，因爲我是新來的軌道。由於這個原因，數據提取似乎並不正確。

這是我有： 就業：

class Employment < ActiveRecord::Base 
    belongs_to :group 
    belongs_to :employee 
end 

部：

class Department < ActiveRecord::Base 
    belongs_to :group 
    belongs_to :user 
end 

用戶：

class User < ActiveRecord::Base 
    has_many :departments 
    has_many :groups, :through=>:departments 

    has_many :employees, :through=>:departments, :source => :group 
end 

組：

class Group < ActiveRecord::Base 
    has_many :departments #new 
    has_many :users, :through => :departments #new 

    has_many :employments 
    has_many :employees, :through => :employments 
end 

員工：

class Employee < ActiveRecord::Base 
    has_many :employments 
    has_many :groups, :through => :employments 
end 

我覺得我有最大的問題是要弄清楚如何獲得total employees給用戶。在SQL它會與此查詢工作：

select * from employees where id in (select employee_id from employments where group_id in (select group_id from departments where user_id = 4)) 

Answer 1

這可能會爲你工作...

class User < ActiveRecord::Base 
    has_many :departments 
    has_many :groups, :through=>:departments **, :include => :employee** 

    has_many :employees, :through=>:departments, :source => :group 
end 


User.find(4).groups.collect { |c| c.employee.size }