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**Category:** Rails\
**Created:** [July 14, 2007, 11:39pm UTC](https://www.ruby-forum.com/t/observe-field-does-this-generate-html/109437 "2007-07-14T23:39:40Z")\
**Posts on this page:** 4\
**Page:** 1
**Author:**  [@mcampbell](https://www.ruby-forum.com/u/mcampbell)\
**Post date:** [July 14, 2007, 11:39pm UTC](https://www.ruby-forum.com/t/observe-field-does-this-generate-html/109437/1 "2007-07-14T23:39:40Z")
I don’t have Rails installed at the moment, I’d like to check myself,
but it’s just a simple curiosity.
observe\_field fits into replacement tags \<%= %\>, which caught my
attention because as far as I know it’s just javascript observing a
field and should not stick anything into HTML. Is \<%= merely used as an
enabling method, or will there actually be some sort of HTML object
there?
Also, does the observer have to come after the field it is observing or
can I stick them all at the top of the HTML?
Thanks.
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**Author:**  [@mcampbell](https://www.ruby-forum.com/u/mcampbell)\
**Post date:** [July 14, 2007, 11:50pm UTC](https://www.ruby-forum.com/t/observe-field-does-this-generate-html/109437/2 "2007-07-14T23:50:35Z")
Michael C. wrote:
> I don’t have Rails installed at the moment, I’d like to check myself,
> but it’s just a simple curiosity.
Install Rails, Firefox, & Firebug, and try it.
> observe\_field fits into replacement tags \<%= %\>, which caught my
> attention because as far as I know it’s just javascript observing a
> field and should not stick anything into HTML. Is \<%= merely used as an
> enabling method, or will there actually be some sort of HTML object
> there?
When I use a \<%= form\_remote\_for … %\>, and when I run my site in
Firefox,
point my mouse to the form, and get the “Context Menu” (the “right”
mouse
button), Firebug has a feature “inspect element”. This shows the form in
a
panel of my browser, like this:
The \<%%\> part turned into a big splatch of JavaScript, calling the
Prototype.js (or Scriptaculous?) method Ajax.Request. And that hides all
the
ugly magic required to send the ajax commands to my controller ‘ring’,
action ‘set\_attack\_mode’.
The observe\_field stuff must work the same general way - a Rails method,
in
Ruby, wrapping a Scriptaculous method, in JavaScript.
> Also, does the observer have to come after the field it is observing or
> can I stick them all at the top of the HTML?
Put them near their observers, so they are clear to read.
–
Phlip
[http://www.oreilly.com/catalog/9780596510657/](http://www.oreilly.com/catalog/9780596510657/)
“Test Driven Ajax (on Rails)”
assert\_xpath, assert\_javascript, & assert\_ajax
---
**Author:**  [@mcampbell](https://www.ruby-forum.com/u/mcampbell)\
**Post date:** [July 15, 2007, 12:23am UTC](https://www.ruby-forum.com/t/observe-field-does-this-generate-html/109437/3 "2007-07-15T00:23:04Z")
I know form\_remote\_for generates HTML, of course 🙂 That’s implied
considering there’s a form to be generated. I was asking specifically
about observe\_field and observe\_form considering they go into a \<%= tag
yet there’s no apparent HTML that should be generated.
I was just looking for a quick answer from someone who already used the
helper, I can certainly check myself later, no biggie.
---
**Author:**  [@mcampbell](https://www.ruby-forum.com/u/mcampbell)\
**Post date:** [July 19, 2007, 6:07am UTC](https://www.ruby-forum.com/t/observe-field-does-this-generate-html/109437/4 "2007-07-19T06:07:26Z")
observe\_field and observe\_form both generate SCRIPT elements
containing that Javascript.
On Jul 14, 3:23 pm, Michael C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)