Question

i 有三个模式:

location, user, discovered_location(location_id,user_id)

我认为,如果用户发现该地点,就需要一个外部加入,以便进入所有地点,并包括所发现的“地点模式”。

我需要的是<代码>{地点1,地点2,地点3:includes 发现_ 所在地,地点4 页: 1

Is there a Rails 3 way to do that ? If not, what is the best way ?

EDIT

I want to get the locations specified above, for a certain user. To better illustrate, it should be :

<用户代码>{ 地点1, 地点2, 地点3:includes 发现: 地点4 页: 1

(用户有许多发现地点)

Answer 1

你们需要检查一下,在你发现的“地点表”中,用户要么等于有关用户的id,要么无效。可在meta_处上完成。 gem。鉴于以下模式:

class User < ActiveRecord::Base
  has_many :discovered_locations
  has_many :locations, :through => :discovered_locations
end

class Location < ActiveRecord::Base
  has_many :discovered_locations
  has_many :users, :through => :discovered_locations
end

class DiscoveredLocation < ActiveRecord::Base
  belongs_to :user
  belongs_to :location
end

插入一些 du数据,然后作如下陈述:

Location.includes(:discovered_locations).where(
  {:discovered_locations => {:user_id => User.first.id}} | 
  {:discovered_locations => {:user_id => nil}}
).each do |loc|
  puts "#{loc.name} #{loc.discovered_locations.empty? ?  not visited  :  visited }"
end

Answer 2

You can do an outer join in Rails only by using an SQL literal in the joins method:

joins("OUTER JOIN table2 on table2.column = table1.column")

Answer 3

。

http://guides.rubyonrails.org/active_record_querying.html#specification-conditions-on-eager-loaded-associations” rel=“nofollow”>http://guides.rubyonrails.org/active_record_querying.html#specification-conditions-on-eager-loaded-associations

友情链接