nested include

嵌套使用rails find :include選項
nested include in rails
弄幾個 example 就懂啦

<br />class InventoryLine <br /> belongs_to :item <br /> belongs_to :swap <br />end <br /><br />class Swap<br /> belongs_to :person<br /> belongs_to :source, :class_name => “Person”, :foreign_key => :source_id<br /> belongs_to :destination, :class_name => “Person”, :foreign_key => :destination_id<br />end<br /><br />class Person<br /> has_many :swaps<br /> has_many :swaps_as_source, :class_name => “Swap”, :foreign_key => :source_id<br /> has_many :swaps_as_destination, :class_name => “Swap”, :foreign_key => :destination_id<br />end<br /><br />#{:first_table => :second_table}<br /> @inventory_lines = InventoryLine.find(:all, :include => [{:swap => [:source, :destination]}, :item])<br /><br />#如果你只有include 一個association 的話, 沒問題<br />Person.find(:all, :include => :swaps_as_source, :conditions => "swaps.destination_id IS NOT NULL")<br /><br />#如果你include 了兩個 association 卻又是對應到相同的table 就要小心了, 第一個include 的仍然是用table name, 但是後面的就是本身的複數的 association 加上parent table name<br />Person.find(:all,<br /> :include => [:swaps_as_source, :swaps_as_destination],<br /> :conditions =><br /> "swaps.destination_id IS NOT NULL AND<br /> swaps_as_destinations_people.source_id IS NOT NULL"<br />#因為是在people table 做search<br />#swaps_as_destination 複數 加上 people<br />)<br /><br />