How to validate in this case?

My application has the following models:


(and others that are irrelevant to the question)

In a Form, I have many Fields and for a Field, there are many Forms. The
idea is to generate a form with customizable Fields. The Field has an
attribute called "type" that defines what control will be rendered
(input:text, input:checkbox, etc) and "format", that defines what data
validation will be made. It can be a date, a phone number or something

The FieldForm has attributes to reference Field and Form, and also
max_length, min_length, unique and required, as well. These attrs are
there because they don't depend directly on Field type and can vary
between forms.

The unique attribute is specially critical. It allow the user to specify
what field will be used to check duplicities (for example, denying a
user to register a form with the same email twice). It's a boolean field
and for a Form, just one field will be "unique".

The Value model is a simple dictionary to use with the Fields that are
radio, select or checkbox. A Field can have many Values.

Finally, the Record model has attributes to save the reference of a
FieldForm, the reference of a Value and a data field that corresponds to
the user input, if Field is something that can be manually entered,
there is no need to reference Value, so it can be null or zero.

Well... The complicated part comes now. I haven't idea on how to
implement the validation. If the validation is done in the controller, I
don't know how to show the errors that could happen (errors.add_to_base
doesn't work because 'errors' object belongs to the model). If the
validation is done in the model, I'll mighty be breaking 50% of the MVC
rules by including references of other models into the Record model

For instance, this is the method I use to check duplicates:

(actually it is part of Records controller)

  def _exists_by_unique? form, records

    data = nil

    unique_field = FieldForm.where(:form_id =>, :unique =>

    if not records or not unique_field



      records.each do |record|

        if record.field_form_id ==

          data =



      if data

        Record.exists? ["field_form_id = ? AND data = ?",, data ]




It returns true if the record is duplicate or false if it is not or
there is no unique field defined.

I think it's pretty absurd to put this method in the model! And so the
further validations the Records must do before saving into the db, like
checking if is in
field_form.min_length..field_form.max_length and if
if field_form.required == true...

So, any suggestions to help me?

[ Please, have patience with me! I'm about 1 month working with Rails.
Sorry for the english errors! ]

So the record corresponds to what is entered by a user filling in one
of these generated forms and what you are trying to do is check that
they have filled in the form respecting all the constraints setup for
that form?


Don't use 'type' as an attribute, it will cause you grief. Rails will
assume you are using STI and you will get some strange errors.



Yes, that's what I want to do.


That's just an alias for the post. In the model, its real name is



That is ok then. When posting questions it is best to stick as closely
as possible to the real problem in order to avoid confusion.



Yes, that's what I want to do.

I'd be tempted to have a non persistent model that contains the set of
choices made by the user and write the validations in this model.
If you use the ActiveModel stuff for your validations it should be
just like writing validations on a normal model, will play nicely with
form helpers etc.