Refresh a page using AJAX?

Rails
1

Hai friends,

I want to know how a part of the webpage (data obtained from
database) can be refreshed at periodic intervals(say 5 sec).
I have tried periodically_call_remote() method.But it is not working
for me.

<% periodically_call_remote(:url => { :action =>
:show_readings_for_station },
:frequency => 5, :update => “reading_list”)%>

#my code here which obtains data from database

show_readings_for_station is a method in the controller…

Thanks,
Veena

2

On 15 Mar 2010, at 13:28, Veena J. wrote:

show_readings_for_station is a method in the controller…

You need to render the periodical executer in the page, so two things
that should do it:

  • Add the call to periodical updater after your div element
  • use <%= instead of just <%
# render the partial here, render the same partial from your show_readings_for_station method
<%= periodically_call_remote(:url => { :action => :show_readings_for_station }, :frequency => 5, :update => "reading_list")%>

Best regards

Peter De Berdt

3

Veena J. wrote:

I want to know how a part of the webpage (data obtained from
database) can be refreshed at periodic intervals(say 5 sec).
I have tried periodically_call_remote() method.But it is not working
for me.

<% periodically_call_remote(:url => { :action =>
:show_readings_for_station },
:frequency => 5, :update => “reading_list”)%>

#my code here which obtains data from database

show_readings_for_station is a method in the controller…

Just to be sure, you did put:

<%= javascript_include_tag :defaults %>

inside your section right?

4

Hai Robert,
Thanks for your help.I have done what you have told me.But the problem
is it refreshes only for the first time and shows some RJSerror on the
webpage.

readings controller

def show_current_readings
@range=ConfigureParameter.find(:all)
if (params[:state] =="")
@readings = CurrentReading.find(:all)
else
stations = Station.find_all_by_state(params[:state])
@readings=
CurrentReading.find_all_by_station_id(stations,:order=>“station_id”)
end
render :update do |page|
page.replace_html :current_reading,
:partial=>‘current_readings_list’
end
end

readings/index.html.erb

<% form_for :selected_district ,:url => {:action =>‘update’,:id =>
@selected_district } do |f| %>

<%= f.label :Stations %> <%= select(:selected_district,:state, @states,{:include_blank=>'All'},{:onchange =>remote_function(:url=>"/readings/show_readings_for_station",:with =>"'state='+this.value")} ) %> <%end%>
<% form_tag :action =>"details" do %>
#code here
<%= periodically_call_remote(:url => { :action=> :show_current_readings }, :frequency => 5, :update =>"current_reading")%>

_current_readings_list.html.erb

#this partial has the code which is inside the “current_reading” div tag

I am attaching the error generated on the webpage also.

Please help me

Thanks
veena

5

I agree with Naren.

Sending name of the div - “current_reading” as the :update option in the
ajax call is enough to automatically replace the contents. No need for
explicitly calling replace_html in the action.

However if you want to use replace_html in your action…

do not send <%= periodically_call_remote(:url => { :action=>
:show_current_readings
}, :frequency => 5, :update =>“current_reading”)%>

:update=>“current_reading”

good luck,
Nitin.

On Wed, Mar 17, 2010 at 12:16 PM, Narendra sisodiya <

6

Hi Veena,

You are mentioning :update attribute in the ajax call, so in the
responding
action you do not need to replace the content of the div. Rails will
automatically update it.

use following code in your controller

 render :partial=>'current_readings_list'

or the second solution is just remove the :update attribute from the
ajax
call it will run properly.

~Naren

7

Veena,

be clear, you want the page to refresh or the div?

8

Hai Nitin,
Now I have made the following changes in my code.But the page is not
refreshing at all.What could be the problem?

readings controller

def show_current_readings
@range=ConfigureParameter.find(:all)
if (params[:state] =="")
@readings = CurrentReading.find(:all)
else
stations = Station.find_all_by_state(params[:state])
@readings = CurrentReading.find_all_by_station_id(stations,
:order=>“station_id”)
end
render :update do |page|
page.replace_html :current_reading,
:partial=>‘current_readings_list’
end
end

readings/index.html.erb

<%= periodically_call_remote(:url => { :action=> :show_current_readings
}, :frequency => 5)%>

_current_readings.html.erb

#code inside “current_reading” div tag

Thanks
Veena

9

have you included all necessary js files? which prototype your using for
Ajax?
copy & paste the development.log file

10

and one more thing, please install firebug for firefox if your using,
and
investigate how it requests the server.

11

Bala wrote:

Veena,

be clear, you want the page to refresh or the div?

I want only apart of the page to be refreshed which is inside div

12

Hai Bala,

  I hav looked into the development.log file.I understood that the

problem as in “_current_readings_list” it is not getting the id
parameter based on which it has to display the readings.I dont know
whether i am correct or not.

I am attaching the development.log file.

controller
def show_readings_for_station
@range=ConfigureParameter.find(:all)
if (params[:state] =="")
@readings = CurrentReading.find(:all)
else
stations = Station.find_all_by_state(params[:state])
@readings = CurrentReading.find_all_by_station_id(stations,
:order=>“station_id”)
end
respond_to do |format|
format.js
end #End of respond_to do block
end #End of action show_readings_for_station

def show_current_readings
@range=ConfigureParameter.find(:all)
if (params[:state] =="")
@readings = CurrentReading.find(:all)
else
stations = Station.find_all_by_state(params[:state])
@readings = CurrentReading.find_all_by_station_id(stations,
:order=>“station_id”)
end
render :update do |page|
page.replace_html :current_reading,
:partial=>‘current_readings_list’
page.visual_effect :highlight, ‘current_reading’
end
end

index.html.erb

<% form_for :selected_district ,:url => {:action =>‘update’,:id =>
@selected_district } do |f| %>

<%= f.label :Stations %>

<%= select(:selected_district,:state,
@states,{:include_blank=>‘All’},{:onchange
=>remote_function(:url=>"/readings/show_readings_for_station",:with
=>"‘state=’+this.value")} ) %>

<%end%>

<% form_tag :action =>"details" do %>
# code here
<%= periodically_call_remote(:url => { :action=> "show_current_readings" }, :frequency => 5)%> <%end%>

Can you plz tell me how can i get the id of the selected element in
select tag to the action “show_current_readings”? If i am wrong plz do
correct me…

Thanks,
Veena

13

you need to include a option
,
:with=>"‘state=’+document.getElementById(‘selected_district_state’).value")

for your periodically call control…
<%= periodically_call_remote(:url => { :action=>“show_current_readings”
},
:frequency => 5,
:with=>"‘state=’+document.getElementById(‘selected_district_state’).value")
%>

I will send more hints later.
Nitin

14

Veena,

can you post the current_readings_list codes

i think you miss the point. when you call the partial file through
controller, you must pass the value through locals if the varaible is
not
instance

something like this

page.replace_html :current_reading, :partial=>‘current_readings_list’,
:locals => {:id => params[:id]}

15

Thank you soooooooooo much Nitin. Your thing has solved my problem…
Now i am getting the id of the selected state to the
“periodically_call_remote()”

Thank you Bala for giving so much of help…
Thank you all…

Guys you are really great…

Thanks,
Veena

16

sure keep learning…
Nitin.

17

welcome.