has_many通过关联依赖destroy条件下谁调用destroy [英] has_many through association dependent destroy under condition of who called destroy
问题描述
有没有办法在 before_destroy
钩子中检查称为 destroy
的对象(类)?
Is there a way to check, within a before_destroy
hook, what object (class) called destroy
?
在下面的例子中,当一个 patient
被销毁时,他们的 appointments
也会被销毁(这是我想要的);但是,如果有任何与 physician
相关的 appointments
,我不想让 physician
被销毁.
In the following example, when a patient
is destroyed, so are their appointments
(which is what I want); however I don't want to allow a physician
to be destroyed if there are any appointments
associated with that physician
.
再说一次,有没有办法在 before_destory
回调中进行这样的检查?如果没有,有没有其他方法可以根据呼叫的方向"(即根据呼叫者)来完成这种破坏检查"?
Again, is there a way to do such a check in the before_destory
callback? If not, is there any other way to accomplish this "destruction check" based on the "direction" of the call (i.e. based on who called)?
class Physician < ActiveRecord::Base
has_many :appointments, dependent: :destroy
has_many :patients, through: :appointments
end
class Patient < ActiveRecord::Base
has_many :appointments, dependent: :destroy
has_many :physicians, through: :appointments
end
class Appointment < ActiveRecord::Base
belongs_to :patient
belongs_to :physician
before_destroy :ensure_not_referenced_by_anything_important
private
def ensure_not_referenced_by_anything_important
unless patients.empty?
errors.add(:base, 'This physician cannot be deleted because appointments exist.')
false
end
end
end
推荐答案
就说:
class Physician < ActiveRecord::Base
has_many :appointments, dependent: :restrict_with_exception
has_many :patients, through: :appointments
end
注意dependent: :restrict_with_exception
.这将导致 Active Record 拒绝销毁任何与约会记录相关联的医师记录.
Note the dependent: :restrict_with_exception
. This will cause Active Record to refuse to destroy any Physician records that have associated Appointment records.
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