Summary of form validation methods

Is there a summary anywhere of data entry form validation techniques for
Rails apps? I’ve come across lots of snippets of advice but they are all
so far-flung that it’s hard to sit down and organize an approach. The
kind of thing I’m looking for would be a simple list with entries like:

validates_presence_of

  1. simplest: Make sure your table model contains a line like
    validates_presence_of :LoanID, :message => “is missing”
    This will catch the error after the form is submitted by the user.
  2. Use JavaScript to check for null in this field (onchange ?)
  3. Use DrySQL… (when does this catch the error?)
  4. Others?

In other words, I’d like to see a summary of techniques for each type of
validation that can be applied to a data entry field. Then I (or the
rest of you!) will be able to pick and choose among the techniques which
are best for the particular situations at hand.

Maybe a full discussion of this calls for an article or even a whole
book, but all I’m looking for is a summary to help me decide among
techniques. The list would serve as a starting point for further
research into the techniques that seem best.

Can anyone help with this?

Shauna

Hello Shauna,

  1. Use JavaScript to check for null in this field (onchange ?)
  2. Use DrySQL… (when does this catch the error?)
  3. Others?

I don’t know much about DrySQL, but I’m sorry to say your
approach doesn’t make sense. Validation rules must be part
of your model, so use Rails validations or customized
validations. Keep in mind that your datas can be used
through web clients or other means : WebServices, REST api…
So imagine that you decide to do only JavaScript checks
on the client side (let’s keep away the JS disactivation pb),
without using rails validations, what will happen if you corrupt
your datas, say during a migration ?

So use Rails validations, then decide if you want client-side
validation with JS to improve the client experience.

In other words, I’d like to see a summary of techniques for
each type of validation that can be applied to a data entry field.
Then I (or the rest of you!) will be able to pick and choose
among the techniques which are best for the particular
situations at hand.

I don’t think such a summary exist. You can’t trust client
side validation. Do your server-side validations, add if needy
client-side (JS) validation/checking.

Just my 2 cents,

– Jean-François.


À la renverse.

Thanks, Jean-François, the client-side vs. server-side issue was on my
mind and your reply helps. (I haven’t tried DrySQL yet - just got that
info from the author’s blog but he claims that DrySQL “automatically
generates validations for ActiveRecord data classes that enforce the
constraints declared on your DB”).
http://allyourdatabase.blogspot.com/search/label/ruby-smalltalk

So use Rails validations, then decide if you want client-side
validation with JS to improve the client experience.

Yes, thanks for the reminder. In addition to Rails validations, I need
to make up on-line forms that are as robust as our desktop version.
Waiting until the whole form is submitted to check all the fields is
unacceptable, and running back to the server for every field entered
seems extreme. So I’d like to do some combination of client-side (for
the simpler things like “is it blank when it shouldn’t be?”) and
server-side (like "does this Loan name already exist?). I can divide up
some forms so that crucial identifying fields are collected separately
first, then if all that passes muster the rest of the fields are
presented.

But what I really want to have is some awareness and comparison of what
techniques are out there, and if there are different techniques
available for different types of validation or types of input fields
(like radio buttons or drop-down lists). I’ve googled around but such
info is really scattered and it’s hard to get a handle on what the
choices are, let alone how to compare them!

I’ve read that DHTML is unreliable, but unreliable in what way? What are
the consequences of using it? Is it just that it doesn’t work the same
way on all browsers, or that even on one browser it doesn’t always catch
the error, or what?

Is there any more summary info on validations?

Thanks,
Shauna

Teehee. She said DHTML. Where’re my bell-bottoms?

Seriously though, relying on JavaScript methods without providing
alternate
methods of getting things done [for those who have JS disabled, etc] is
the
biggest concern. You’ve got to make a call on exactly how important that
is
to you. Not to call anybody out but I noticed that even Backpack
disables
some functionality when you turn off JS. Most of their users probably
wouldn’t do something that strange but they might for your app. That
[plus
the differences between DOM structures and JS functions between
browsers]
would be the main worry I’d have.

As far as simple validation goes. Sure, use JS to validate it on the
client-side. If they’re not using it then make sure the model validates
it
as well. I wouldn’t assume the user is JS-enabled. Not when there’s so
safe
and sure a client-side solution.

RSL

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