# Table relations from forms

**URL:** <https://www.ruby-forum.com/t/table-relations-from-forms/88846>\
**Category:** Rails\
**Created:** [March 14, 2007, 11:31pm UTC](https://www.ruby-forum.com/t/table-relations-from-forms/88846 "2007-03-14T23:31:34Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![bart](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/f19dbf/32.png) [@bart](https://www.ruby-forum.com/u/bart)\
**Post date:** [March 14, 2007, 11:31pm UTC](https://www.ruby-forum.com/t/table-relations-from-forms/88846/1 "2007-03-14T23:31:34Z")

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Hi,

I started with Ruby on Rails a few weeks ago and am looking for a  
‘best practice’ to handle the creation of objects that relate to  
eachother. I will illustrate it with an example:

My model consists of 2 classes that are related, a model  
Businesspartner and a model Ticket. Every ticket belongs\_to one  
Businesspartner, a businesspartner has\_many tickets. The form to  
create a new Ticket is different for different kind of users. Users  
that have a role “customer” don’t see anything for this relation (it  
is assigned when creating the ticket), users with the role “employee”  
get a select list of all businesspartners. There are a few things I  
want to check on creating a new ticket:

\*Check excistence of the supplied businesspartner by the form:  
preventing illegal input  
\*Check if the user is a customer if this is true set the  
businesspartner to the default for this user: ignore the fields in the  
param hash

Is there a best practice how to implement a thing like this? Should it  
be implemented in the controller or model? And are validation’s  
usefull for this or should I handle it in the constructor or use a  
separate method?

Currently I created a method in the model that processes the logic and  
returns a check instance of the Ticket , this works fine but I don’t  
see a nice way to notify the user that one of the related fields isn’t  
correct (I can’t access the errors variable the way that validations  
can). I guessed this is a common challenge but haven’t find any best  
practice on it yet.

Best regards,

Bart

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<div class="post-metadata">

**Author:** ![bart](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/f19dbf/32.png) [@bart](https://www.ruby-forum.com/u/bart)\
**Post date:** [March 15, 2007, 12:05am UTC](https://www.ruby-forum.com/t/table-relations-from-forms/88846/2 "2007-03-15T00:05:38Z")

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On Wed, Mar 14, 2007 at 10:30:24PM -0000, Bart wrote :

> My model consists of 2 classes that are related, a model  
> Businesspartner and a model Ticket.

Assuming you have your models:

class Businesspartner \< ActiveRecord::Base  
has\_many :tickets  
end

class Ticket \< ActiveRecord::Base  
belongs\_to :businesspartner  
end

> be implemented in the controller or model? And are validation’s  
> usefull for this or should I handle it in the constructor or use a  
> separate method?

First of all, the logic ‘user is a customer’ should be in your model.  
I would create a method is\_a\_customer in the User model so whenever I  
want to change conditions for a user to be a customer, I have to change  
it in a single place:

def is\_a\_customer?  
#Your conditions, like (assuming users.customer is a boolean row):  
self.customer  
end

So, you could write in your controller:

def create  
@user = User.find(session[id])  
@businesspartner =  
Businesspartner.find\_by\_name(params[:businesspartner])  
unless @businesspartner  
if @user.is\_a\_customer?  
@user.businesspartner = @businesspartner  
else  
# I don’t know, may be  
params.delete(:businesspartner)  
#blablabla  
end  
else  
flash[:error] = ‘Illegal input!’  
redirect\_to :action =\> :index  
end  
end

Hope that helps,

–  
,========================.  
| Pierre-Alexandre M. |  
| email : removed\_email\_address@domain.invalid |  
`========================’

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<div class="post-metadata">

**Author:** ![bart](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/f19dbf/32.png) [@bart](https://www.ruby-forum.com/u/bart)\
**Post date:** [March 19, 2007, 8:12pm UTC](https://www.ruby-forum.com/t/table-relations-from-forms/88846/3 "2007-03-19T20:12:31Z")

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Thanks for your input! I have many different roles users can have, so  
this can  
become quite long. Suppose I create a Ticket object from something  
other than  
this controller (or method) then I would have to repeat the same  
checking. That’s  
why I thought it would be better to implement this in the model, do  
you see any drawbacks  
on this aproach?

I have also thought of implementing this as a validator; invalid  
objects can be created but  
never saved and I thought displaying the error messages could be done  
in the same  
way other validators do this, which seems logical and consistent to  
me. Or am I missing  
some drawbacks on this aproach?

Bart