How to subclass active record to call a method on all save and destroy actions

Rails
1

I’m looking for a way to subclass active record (I’ll refer to the
subclass I want to create as NewActiveRecord) so that I can call
different methods on a save or destroy action on all models which sub
class NewActiveRecord

I dont want to use before_save or any of the other regular call back
methods as I want to be able to use these call backs in the models
which subclass NewActiveRecord without having to call super everytime
I use them.

Anyone have any ideas about how I can do this?

Cheers

Tony

2

On 10/24/07, teesea [email protected] wrote:

I’m looking for a way to subclass active record (I’ll refer to the
subclass I want to create as NewActiveRecord) so that I can call
different methods on a save or destroy action on all models which sub
class NewActiveRecord

I dont want to use before_save or any of the other regular call back
methods as I want to be able to use these call backs in the models
which subclass NewActiveRecord without having to call super everytime
I use them.

Use ActiveRecord::Observer instead of ActiveRecord::Callbacks?

http://www.robbyonrails.com/articles/2007/04/28/q-a-activerecord-observers-and-you
http://api.rubyonrails.org/classes/ActiveRecord/Observer.html

3

You probably want to set self.abstract_class = true.

Fred

4

Thanks for the observer link, they would work nicely but I need to be
able to stop a model from saving or destroying, if the additional
method i call returns false.

Basically what I’m trying to do is add some authentication methods
into all my active record models so that whenever a save or destroy,
and also a association is added the authentication method checks that
the user has privileges to do this.

@Frederick

Thanks, I’ve heard that using self.abstract_class = true will allow me
to sub class ActiveRecord, I need to know which single method in
ActiveRecord is best to override to add the authentication methods. Do
you know which would be best?, or could you point me in the direction
of some good resources on ActiveRecord

Cheers

Tony

On Oct 24, 8:34 pm, Frederick C. [email protected]

5

On 10/25/07, teesea [email protected] wrote:

could you point me in the direction
of some good resources on ActiveRecord

For extending ActiveRecord the fairly new “Pro ActiveRecord” book from
APress is pretty good.

I’m not sure I’d recommend it for an introduction/only reference to AR
(AWDR 2ed does a better job IMHO) but for advanced things like
extending AR, it’s the best resource I’ve found as yet.

Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/

6

Thanks to all those who responded

I’ll have a look at acts_as_paranoid and see what the best way forward
is

7

We don’t do that kinda stuff in the Ruby world.

We use modules instead, so we can “mix in” that behavior.

In lib/ar_extentions.rb

module MyActiveRecordExtentions

def save(*args)
if some_condition
super(*args) # do the original
else
return false # or do your own stuff
end
end

def destroy
return false
end

end

Then all I need to do is

class User < ActiveRecord::Base

include MyActiveRecordExtensions

end

If you really want to see how this works in action, take a look at the
acts_as_paranoid plugin. It uses this technique to mark records as
deleted
instead of actually deleting them, by overriding the destroy method.
It’s a
good place to start learning about this kinda stuff.