Rails - Feb 2010 - Using Rails form helpers on non-existent methods

Normally, when using form helpers in Rails, each field directly
correlates to a method on the appropriate object.

However, I have a form (user signup) that needs to include fields that
are not part of the user model itself (for instance, card details) but
need to appear.

How can I build the form so that I can get the necessary fields, and
validate them as I need to (so that it fits with all my other
validations) without dirty-ing my user model?

Essentially I''m not building a form that directly correlates to the
model in question. For instance a signup form might incorporate some
user properties, and some "throw away" properties (such as those you
might fire at a CC gateway and then forget).

If I created attributes on my user model, I would always need to
supply those properties for validations to pass whereas I only want to
validate these items on this single form in this single location.

What''s the approach to take here?

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You can use attr_accessor to create new model attributes that are not 
present in the database.

For example, lets say you want to have a field "password" that the
user
types in, but this field is not going to be stored in the database. 
Instead the table will have a field "encrypted_password" that is
created
from the "password" field that the user submits.

class User < ActiveRecord::Base
  # create a ''virtual'' attribute
  attr_accessor :password

  # validate its presence only when creating a new record
  validates_presence_of :password, :on => :create

  # set the database field "encrypted_password" based on
"password"
  before_create :encrypt_password

  private

  def encrypt_password
    #set encrypted PW with industrial strength encryption
    self.encrypted_password = self.password.reverse
  end

end
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Neil Middleton wrote:
> Normally, when using form helpers in Rails, each field directly
> correlates to a method on the appropriate object.
> 
> However, I have a form (user signup) that needs to include fields that
> are not part of the user model itself (for instance, card details) but
> need to appear.
> 
> How can I build the form so that I can get the necessary fields, and
> validate them as I need to (so that it fits with all my other
> validations) without dirty-ing my user model?
> 
> Essentially I''m not building a form that directly correlates to
the
> model in question. For instance a signup form might incorporate some
> user properties, and some "throw away" properties (such as those
you
> might fire at a CC gateway and then forget).
> 
> If I created attributes on my user model, I would always need to
> supply those properties for validations to pass whereas I only want to
> validate these items on this single form in this single location.
> 
> What''s the approach to take here?
If you can''t use a virtual attribute as Sharagoz described, then you 
probably want to put the extra fields in a separate model and use 
accepts_nested_attributes_for or something.

Best,
-- 
Marnen Laibow-Koser
http://www.marnen.org
marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org

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