# Moving code to model from controller

**URL:** <https://www.ruby-forum.com/t/moving-code-to-model-from-controller/147679>\
**Category:** Rails\
**Created:** [September 4, 2008, 7:52am UTC](https://www.ruby-forum.com/t/moving-code-to-model-from-controller/147679 "2008-09-04T07:52:36Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![sijo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/da6949/32.png) [@sijo](https://www.ruby-forum.com/u/sijo)\
**Post date:** [September 4, 2008, 7:52am UTC](https://www.ruby-forum.com/t/moving-code-to-model-from-controller/147679/1 "2008-09-04T07:52:36Z")

</div>

Hi  
Last day I read an article says that business logic should be in  
model Till now my coding method was writing complete code in controller  
and nothing in model I would like to change that style. Sorry now only  
I became aware of that, since I am not an expert programmer and also and  
of self learning process. My current code in controller is as below  
This for creating a problem

def create  
begin  
ActiveRecord::Base.transaction do  
@problem=Problem.new(params[:problem])  
@problem.save!  
@problem.update\_attribute(“number”,“PB”+ @problem.id.to\_s)  
end #end of transaction  
rescue ActiveRecord::ActiveRecordError =\> e:  
puts ‘Error’ +e.to\_s  
render :action =\> ‘create\_ui’  
else  
redirect\_to(:action =\> ‘show\_problem\_ui’, :id =\> @problem.id)  
end #end of begin  
end

```
   Could anybody please tell me how can I shift the above code to

```

Problem model and follow the proper MVC pattern .The above code is  
minimal but in almost all parts of the code I have followed the same  
pattern ie write complete code in controller And if I get any good rails  
programming practises links that will be helpful

Thanks in advance  
Sijo

---

<div class="post-metadata">

**Author:** ![sijo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/da6949/32.png) [@sijo](https://www.ruby-forum.com/u/sijo)\
**Post date:** [September 4, 2008, 1:40pm UTC](https://www.ruby-forum.com/t/moving-code-to-model-from-controller/147679/2 "2008-09-04T13:40:34Z")

</div>

In this case, the only thing that the controller is doing that the model  
could/should is setting the problem number. Since the problem number  
should  
be set any time a problem is created, move that logic into an  
after\_create  
callback inside the model.

class Problem \< ActiveRecord::Base  
…  
after\_create :set\_problem\_number  
…  
private

def set\_problem\_number  
self.number = “PB#{self.id}”  
save!  
end  
end

I’d use a callback in the model instead of using an observer in this  
case  
because setting the problem number is work done to the model. If, for  
example, we wanted to log a message or send a notification of some kind,  
I’d  
use an observer, since that kind of work is not done to the model.

Whether to move logic to the model is a question you have to ask in each  
case like the one you shared. Sometimes it’s best to move code to a  
place  
other than the model, view or controller. See the Rails Refactoring  
Catalog  
[  
[http://continuousthinking.com/2008/6/3/refactoring-your-rails-application-tutorial-content](http://continuousthinking.com/2008/6/3/refactoring-your-rails-application-tutorial-content)]  
from Zach D.’ talk at RailsConf 2008 for more details.

Regards,  
Craig

---

<div class="post-metadata">

**Author:** ![sijo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/da6949/32.png) [@sijo](https://www.ruby-forum.com/u/sijo)\
**Post date:** [September 5, 2008, 6:00am UTC](https://www.ruby-forum.com/t/moving-code-to-model-from-controller/147679/3 "2008-09-05T06:00:50Z")

</div>

Hi  
Thanks for your reply  
Sijo

---

<div class="post-metadata">

**Author:** ![sijo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/da6949/32.png) [@sijo](https://www.ruby-forum.com/u/sijo)\
**Post date:** [September 5, 2008, 6:27am UTC](https://www.ruby-forum.com/t/moving-code-to-model-from-controller/147679/4 "2008-09-05T06:27:51Z")

</div>

Hi  
I did as you said ie set a callback after\_create as below

def set\_problem\_number  
begin  
Problem.transaction do  
self.number = “PB#{self.i}”  
save!  
end # end of transaction  
rescue Exception =\> e:  
puts ‘Error’ +e.to\_s  
end # end of begin-end  
end

```
In the above to test to get an exception I deliberately wrote

```

self.number = “PB#{self.i}” instead of self.number = “PB#{self.id}”  
So what happens is a new problem record row is created in table but how  
ever its number say for exapme PB77 is not set …So how can I roll back  
that to if any exception happened in the above call back in model?

Sijo

---

<div class="post-metadata">

**Author:** ![sijo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/da6949/32.png) [@sijo](https://www.ruby-forum.com/u/sijo)\
**Post date:** [September 5, 2008, 3:03pm UTC](https://www.ruby-forum.com/t/moving-code-to-model-from-controller/147679/5 "2008-09-05T15:03:23Z")

</div>

Once you correct the code, it won’t cause any more exceptions. 🙂 Also,  
since you’re using the after\_create callback, your code is running after  
the  
Problem record has been created. Hence, there’s nothing you can do to  
prevent the Problem record from being created.

An additional note: the transaction in the callback is unnecessary. I  
don’t  
think that it runs in the scope of the creation of the problem record  
that  
you’re doing in the controller, and you’re working with only one object  
and  
database operation in the callback anyway.

Regards,  
Craig