ruby-on-rails - 从has_many :through relation中添加和删除

Question

从Rails关联指南中，他们使用has_many:through演示了多对多关系，如下所示:

class Physician < ActiveRecord::Base
  has_many :appointments
  has_many :patients, :through => :appointments
end

class Appointment < ActiveRecord::Base
  belongs_to :physician
  belongs_to :patient
end

class Patient < ActiveRecord::Base
  has_many :appointments
  has_many :physicians, :through => :appointments
end

如何创建和删除约会？

如果我有 @physician，我是否可以编写类似于以下内容的约会来创建约会？

@patient = @physician.patients.new params[:patient]
@physician.patients << @patient
@patient.save # Is this line needed?

删除或销毁的代码呢？另外，如果“患者”不再存在于“约会”表中，会被销毁吗？

Answer 1

在创建约会的代码中，不需要第二行，而是使用#build方法而不是#new:

@patient = @physician.patients.build params[:patient]
@patient.save  # yes, it worked

要销毁约会记录，您只需找到并销毁即可:

@appo = @physician.appointments.find(1)
@appo.destroy

如果要销毁约会记录并销毁患者，则需要在has_many中添加:dependency设置:

class Patient < ActiveRecord::Base
  has_many :appointments
  has_many :physicians, :through => :appointments, :dependency => :destroy
end