refresh a page using AJAX?

rubyonrails-talk
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")%> <div id="reading_list">    #my code here which obtains data from database </div>

show_readings_for_station is a method in the controller.....

Thanks, Veena

2

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 Jose 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")%> <div id="reading_list">    #my code here which obtains data from database </div>

show_readings_for_station is a method in the controller.....

Just to be sure, you did put:

<%= javascript_include_tag :defaults %>

inside your <head></head> 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| %>    <center><b> <%= f.label :Stations %></b> <%= select(:selected_district,:state, @states,{:include_blank=>'All'},{:onchange =>remote_function(:url=>"/readings/show_readings_for_station",:with =>"'state='+this.value")} ) %> </center> <%end%>

<div id="reading_list">   <% form_tag :action =>"details" do %>   <div id="current_reading">    #code here   </div> <%= periodically_call_remote(:url => { :action=> :show_current_readings }, :frequency => 5, :update =>"current_reading")%> </div>

_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

Attachments: http://www.ruby-forum.com/attachment/4591/1.rar

5

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

6

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.

7

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

8

Veena,

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

9

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

10

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

11

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

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| %>    <center><b> <%= f.label :Stations %></b>

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

</center>

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

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

Attachments: http://www.ruby-forum.com/attachment/4596/development.log

13

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]}

14

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

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.