Ruby on rails开发从头来(五十八)- ActiveRecord基础(自关联)
2009-08-07 14:28
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或许存在这样的情况,在一个表中,一条记录关联到表中的另一条记录,例如,公司中的每个雇员都有上级和下级,而他们同时又是雇员,在Rails中你可以这样使用Employee类:
让我们使用一些数据,这里雇员Clem和Dawn都有上级和下级:
现在我们可以通过关联,来回答“X的下属是谁?”,“Y的上级是谁?”。
class Employee < ActiveRecord::Base belongs_to :manager, :class_name => "Employee", :foreign_key => "manager_id" belongs_to :mentor, :class_name => "Employee", :foreign_key => "mentor_id" has_many :mentored_employees, :class_name => "Employee", :foreign_key => "mentor_id" has_many :managed_employees, :class_name => "Employee", :foreign_key => "manager_id" end
让我们使用一些数据,这里雇员Clem和Dawn都有上级和下级:
Employee.delete_all adam = Employee.create(:id => 1, :name => "Adam") beth = Employee.create(:id => 2, :name => "Beth") clem = Employee.new(:name => "Clem") clem.manager = adam clem.mentor = beth clem.save! dawn = Employee.new(:name => "Dawn") dawn.manager = adam dawn.mentor = clem dawn.save!
现在我们可以通过关联,来回答“X的下属是谁?”,“Y的上级是谁?”。
p adam.managed_employees.map {|e| e.name} # => [ "Clem", "Dawn" ] p adam.mentored_employees # => [] p dawn.mentor.name # => "Clem"
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