# Alias Method Chain in before\_filter

**URL:** <https://www.ruby-forum.com/t/alias-method-chain-in-before-filter/109792>\
**Category:** Rails\
**Created:** [July 19, 2007, 3:16am UTC](https://www.ruby-forum.com/t/alias-method-chain-in-before-filter/109792 "2007-07-19T03:16:03Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![davox](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/90ced4/32.png) [@davox](https://www.ruby-forum.com/u/davox)\
**Post date:** [July 19, 2007, 3:16am UTC](https://www.ruby-forum.com/t/alias-method-chain-in-before-filter/109792/1 "2007-07-19T03:16:03Z")

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Hi all,

```
I have the follow code to trap some exceptions in a controller.

```

The code seems to run fine on my development machine but on  
production, it goes into an infinitely loop (eventually a stack  
overflow) trapping at the create\_without\_jazz() method call. Does  
anyone see a potential problem with the the way I’m handling  
the exceptions? (note: render() is not in the correct context, so I  
couldn’t use around filter). Thanks in advance for all your help.

Pastie: [Parked at Loopia](http://pastie.caboo.se/80106)

class FooBarsController \< ApplicationController

before\_filter(:only =\> :create) do  
class\_eval {  
def create\_with\_jazz  
begin  
create\_without\_jazz()  
rescue Exception =\> e  
render :text =\> ‘error’  
end  
end

```
    alias :create_without_jazz :create
    alias :create :create_with_jazz
}

```

end

def create  
raise ‘foo bar create’  
render :text =\> ‘foo bar’  
end

end

---

<div class="post-metadata">

**Author:** ![davox](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/90ced4/32.png) [@davox](https://www.ruby-forum.com/u/davox)\
**Post date:** [July 19, 2007, 5:28am UTC](https://www.ruby-forum.com/t/alias-method-chain-in-before-filter/109792/2 "2007-07-19T05:28:22Z")

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On 7/19/07, David D. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> ```
> rescue Exception => e
> raise 'foo bar create'
> render :text => 'foo bar'
> 
> ```
> 
> end
> 
> end

Hi David,

I don’t really understand what you’re trying to do here. Why not just  
catch the exception in #create? I’d say it’s blowing the stack in  
production mode because the class is not being reloaded on every  
request (which it is by default in development). Consequently, your  
class\_eval gets run more than once on your controller class.

There are of course workarounds, depending on what you’re trying to  
accomplish. Could you elaborate on that more? Also note that if  
you’re just trying to catch unhandled exceptions, it’s probably easier  
to define #rescue\_action (see docs).

Regards,  
George.

---

<div class="post-metadata">

**Author:** ![davox](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/90ced4/32.png) [@davox](https://www.ruby-forum.com/u/davox)\
**Post date:** [July 19, 2007, 6:08am UTC](https://www.ruby-forum.com/t/alias-method-chain-in-before-filter/109792/3 "2007-07-19T06:08:26Z")

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Hi George,

Thanks for the reply! The primary reason I did it this way was  
because I wanted a generic way to handle exceptions that’s flexible  
enough to allow custom rendering on a per action basis. For instance  
you have a lot of existing code that had to deal with various contents  
(e.g. one controller per content). And you needed to be able to  
blacklist a user and take away all his/her creation rights. You (at  
least me) don’t want to go into each action of each controller to  
inject control logics all over the place. So I came up with this  
cheap way to raise an exception at the model level whenever someone  
(the blacklisted user) tries to save a content (raise in  
before\_save). I will then catch it with the before\_filter as you’ve  
seen above. I guess I can use rescue\_action and filter down the  
actions list based on my exception. Any thoughts on the way I’m  
approaching this problem? I somehow I feel kinda dirty mixing model  
and controller this way. Opinions and comments are welcome!

David