Validation without saving

Rails
1

One of the things that strikes me as odd about the validations as I
understand them to work from AWDWR, is that the validations
themselves are only triggered upon a save.

I brought this up earlier that I am accustomed to doing validations
of data before updating a model with it, but Rails wants to allow the
modification of the model, then only bother to validate it if it is
saved – at least that’s what I’m seeing at this point.

What good does that do unsaved model data? Model data that perhaps
never gets saved to a database, but nonetheless must have validated
data to perform its interim purpose.

What if I bring data in from a web service or a file – isn’t it best
to complain to that source (or log the problem, or whatever) at the
moment the data is accepted, and not some who-knows-when point which
may be tainted by some other process and therefore I lose the ability
to complain to the actual source that provided the bad data?

Looking at the methods in validations.rb, I’m not seeing a method
that gives me arbitrary control over when to invoke validations.

I’m probably still not seeing the whole picture, but I’m getting that
“something’s wrong” feeling.

– gw (www.railsdev.ws)

2

if you create a validate function, which automatically gets called by
rails you can do

my_object.validate

there are 2 others validate_on_create and validate_on_update

the my_object.valid? method should invoke these and any of the
validates_X functions

and if you want something that is unique to this data and that doesn’t
get saved on create your own method
and call my_object.my_method_name

White W.

3

On 11/27/07, Greg W. [email protected] wrote:

What good does that do unsaved model data? Model data that perhaps
that gives me arbitrary control over when to invoke validations.

my_object.valid?