Rails - Jul 2009 - like "observe_field"

I don''t see where this can be done in rails directly, but I am hoping
some creative mind can see how to use dvarious rails pieces to do it.

I need an ajax request like "observe_field" that triggers an action so
as to update something, but rather than a field in a form, I want to
observe a file containing json data on a server, such that when the
data changes, I read it, and perform an action with it to update
something.

Does anyone have any idea how I might accomplish this in RoR? Thanks,
Janna B

Janna Brossard wrote:
> I don''t see where this can be done in rails directly, but I am
hoping
> some creative mind can see how to use dvarious rails pieces to do it.
> 
> I need an ajax request like "observe_field" that triggers an
action so
> as to update something, but rather than a field in a form, I want to
> observe a file containing json data on a server, such that when the
> data changes, I read it, and perform an action with it to update
> something.
> 
> Does anyone have any idea how I might accomplish this in RoR? Thanks,
> Janna B
Hi Janna,

I could be mistaken but I don''t think you can use observe_field in that
way.  It has to observe a DOM ID and the closest I think you could use 
in the DOM Location Object, but am unsure...

I know how you can read JSON data from the file though:

require ''open-uri''
require ''json''

url = ''http://search.twitter.com/trends.json''

buffer = open(url, "UserAgent" => "Ruby-Wget").read

# convert JSON data into a hash
result = JSON.parse(buffer)

trends = result[''trends'']
trends.each do |subject|
  puts subject[''name''] + '' '' +
subject[''url'']
end


If I were having to automate this I would create a rake task that called 
a ruby file such as the one listed here that would read the json data 
from the file, and then update the database with the new information..

You could create a cron task to automate the rake task every 30 minutes 
or 1-hour depending...

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