将导轨范围导轨2.2升级到导轨4.2

Question

我在rails 4＆lt;

中转换rails 2 scope语法时遇到问题

类地区＆lt;的ActiveRecord :: Base的  
has_many：位置  
结束  
 
类位置＆lt;的ActiveRecord :: Base的    
belongs_to：region    
范围：允许，lambda {| p_id |     {：joins =＆gt; “在pl.location_id = locations.id上左加入person_locations pl”，       ：conditions =＆gt; [“pl.person_id =？AND pl.active ='是'”，p_id]}   } 的    
#where pl = person_location   
端

类PersonLocation＆lt;的ActiveRecord :: Base的  
belongs_to：location  
端

类LocationsController＆lt; ApplicationController的   
def指数    
@locations = @ region.locations.permitted（current_person.id）.active.all（：order =＆gt;“name”）      
respond_to do | format |        
format.html #index.html.erb     结束    
结束  
端

• 列表项

Answer 1

也许

scope :permitted, ->(p_id) { joins("left join person_locations pl on pl.location_id = locations.id").where("pl.person_id = ? AND pl.active = 'Yes'", p_id) } 

Answer 2

我会写：

scope :permitted, lambda { |id| 
  joins('left join person_locations pl on pl.location_id = locations.id').
  where(pl: { person_id: id, active: 'Yes' })
} 

或者，如果可以将person_locations的关联添加到Location模型中：

has_many :person_locations

scope :permitted, lambda { |id| 
  joins(:person_locations).where(person_locations: { person_id: id, active: 'Yes' })
}