Best practices - field initialization based on display rules

All,

I have a form with the following field interaction rules.

Given checkbox A,
text field B
text field C

If checkbox A is checked then make text field C equal to the value of
text field B and disable field C.

If checkbox A is unchecked then enable field C.

In order to display a form where I’m manipulating an already existing
object, I have something like this in my RHTML template to display text
field C:

<%= (@obj.field_B == @obj.field_C) ?
text_field(:obj, ‘field_C’, :disabled => ‘true’) :
text_field(:obj, ‘field_C’, :disabled => ‘false’) %>

Should I put this logic in a helper so as to simplify my template and
keep this small bit of business logic out of it?

I already have Javascript that would force this behavior for me given
the checked status of the checkbox - should I just call that Javascript
function in an onLoad() handler?

Should I use an onLoad handler that executes an AJAX call to handle
setting up these fields correctly - then I could just add AJAX calls to
default other fields as well? (seems a little excessive to me).

Thanks,
Wes

On Monday, July 17, 2006, at 7:48 PM, Wes G. wrote:

Should I put this logic in a helper so as to simplify my template and
Thanks,
Wes


Posted via http://www.ruby-forum.com/.


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I would do this in two steps…

First… use your controller to set the proper state of instance
variables so that the rules are enforced when an object is loaded in.
This way you don’t need any JS to play around with the initial settings.
You can also set the enabled/disabled state of controls like this.

Second… I would use the KRJS plugin to enforce the rules once the page
has been loaded. It’s pretty simple to add an AJAX response to an
‘onchange’ event and then embed the RJS in the controller. This keeps
the business logic out of the view.

In theory you could write a JS library that does all the validation on
the client side, but I wouldn’t trust that route. It’s not very DRY.

_Kevin
www.sciwerks.com

Kevin O. wrote:

On Monday, July 17, 2006, at 7:48 PM, Wes G. wrote:

Should I put this logic in a helper so as to simplify my template and
Thanks,
Wes


Posted via http://www.ruby-forum.com/.


Rails mailing list
[email protected]
http://lists.rubyonrails.org/mailman/listinfo/rails

I would do this in two steps…

First… use your controller to set the proper state of instance
variables so that the rules are enforced when an object is loaded in.
This way you don’t need any JS to play around with the initial settings.
You can also set the enabled/disabled state of controls like this.

Second… I would use the KRJS plugin to enforce the rules once the page
has been loaded. It’s pretty simple to add an AJAX response to an
‘onchange’ event and then embed the RJS in the controller. This keeps
the business logic out of the view.

In theory you could write a JS library that does all the validation on
the client side, but I wouldn’t trust that route. It’s not very DRY.

_Kevin
www.sciwerks.com

Kevin,

I take your point on the DRYness of a client-side approach. On the
other hand, what I’m needing to do in the view doesn’t really need any
information from the server so doing a POST just to do AJAX somehow
seems excessive (probably because it’s ingrained in me that doing the
POST is expensive, even though I know it’s not because it’s not the
whole page worth of data going back and forth). But I see your point
and I’d consider an AJAX approach.

However, I’m not sure I get you on this point:

“You can also set the enabled/disabled state of controls like this.”

Do you mean set up a variable in my model to represent the state of the
edit field in my view (e.g. enabled vs. disabled)? If so, I would think
that that sort of thing would belong in a “form model” object (what in
the Java world we call a form bean, which is simply responsible for
tracking the state of form elements).

Thanks,
Wes

On Monday, July 17, 2006, at 9:16 PM, Wes G. wrote:

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Second… I would use the KRJS plugin to enforce the rules once the page

Thanks,
Wes


Posted via http://www.ruby-forum.com/.


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Something like that. I sometimes put code in my views like this…

<%= text_field ‘model’,‘attribute’, :disabled=>@model.some_method %>

this works when the page is first loaded to set the initial state but
you then need to worry about it from then on.

Regarding the AJAX thing… I just do what is easiest to implement and
then optimize it later if it becomes a problem. Using something like
the KRJS plugin, it’s almost trivial to implement this sort of thing.

_Kevin
www.sciwerks.com

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