Tell me how to use ActiveRecord#afeter_add
Now I hava a problem,how can I m开发者_运维技巧ake the callback#after_add receive a reference to the join model in a has_many :through association? my code like this:
class Emergency
has_many :departments, :through => :eme_references, :after_add => Proc.new { |eme_reference| eme_reference.eme_flag = 1}
end
the attribute eme_flag is the model EmeReference's attribute! but in the block ,i get the eme_reference.class is Emergency. I want to set the attribute eme_flag of the model EmeReference. That is my question! cheers!
Presumably Emergency
also has_many :eme_references
in order for the :through
association to work?
In that case, you should be able to attach the callback there:
has_many :eme_references,
:after_add => Proc.new { |emergency, eme_ref| # code here }
The block accepts 2 parameters, the first will be the Emergency
, the 2nd will be the EmeReference
being added.
Perhaps a before_save
callback on EmeReference
can also do what you want in this instance?
I think what you want to do can't be done there.
You could create an after_create hook on departments (I'm assuming Emergency has_many eme_references has_many departments):
class Emergency
has_many :departments, :through => :eme_references
def flag!
eme_flag=1
save
end
end
class Department
after_create :check_emergency
# this allows you to call department.emergency. Will return nil if anything is nil
delegate :emergency, :to =>:eme_reference, :allow_nil => true
def check_emergency
self.emergency.flag! if self.emergency.present?
end
end
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