How to obtain the index of selected item from select box?

veena · March 3, 2010, 6:18am

Hai friends,

I am a newbie in ROR.I hav created a select box which takes value

from the databaseI dont know how to get the id or index of the value
selected.

Controller:

class ReadingsController < ApplicationController
def index
@locations= Station.find(:all,:group => “state”,:order =>“state”)
end
end

View:

<% form_for :station ,:url => {:action => ‘index’,:id => @station } do
|form| %>

<%= form.label :Stations %> <%= form.collection_select("state", @locations, :id, :state) %> <%end%>

I want to display the readings according to the selected state
for eg: If I select “Karnataka” from the select box i should get all the
rows in that table whose state=“Karnataka”

My table schema is as below
create_table “stations”, :force => true do |t|
t.string “name”
t.string “unit_id”
t.integer “sim_no”
t.string “state”
t.string “district”
t.string “province”
t.integer “zipcode”
t.string “latitude”
t.string “longitude”
end

Please give me a reply?

veena · March 3, 2010, 10:36am

use j query or java scripting to do so or you may saw on event change
on
tutorial OK

On Wed, Mar 3, 2010 at 10:48 AM, Veena J. [email protected]
wrote:

@locations= Station.find(:all,:group => “state”,:order =>“state”)
<%end%>
t.string “state”

–
Thanks:
Rajeev sharma

veena · March 3, 2010, 10:57am

I wish to answer your query, but I need to know what you are performing
on
Readings controller’s index page ?
I think you are having a list of all locations irrespective of state
selected pre-displayed on index page.
And on selection of a particular state from Stations collection_select
you
want to recalculate and display list of locations related to only
SELECTED
STATE… maybe after a page refresh or AJAX operation.

Correct me if I am wrong, then you’ll have the solution.

NRJ

veena · March 3, 2010, 1:56pm

Good to know,

Because AJAX is involved and you’re new in rails, I am assuming you want
to
have it work using Prototype library and RJS.

Some pages to let you understand Prototype and JQuery AJAX frameworks in
rails…

http://www.prototypejs.org/
http://wiki.github.com/madrobby/scriptaculous/

Now, things you will need to make AJAX work.
If you happen to have a layout file for your application, it should load
the
javascripts necessary to support AJAX operations.
<%= javascript_include_tag :defaults %> will do it for you. It will
include prototype and effects, etc. javascript files.
But if you do not have any layout file like application.rhtml or
application.html.erb then you may also choose to put
“javascript_include_tag
:defaults” line directly on index.html.erb or index.rhtml file under
your
app/views/readings/index.html.erb or …index.rhtml.
Now we are talking about ReadingsController index action with a list
of
all locations displayed on it in a div with id say - < div
id=“reading_list_div” >
You need one more action which will be take one argument as selected
state
and will populate a new list of locations which are related to THAT
PARTICULAR state and render the new list of locations via AJAX on the
same
index page.
<%= f.collection_select :state,Station.find(:all,:group =>
“state”,:order =>“state”), :id, :name, {:include_blank =>“None”,
:onclick
=> remote_function(:url =>“/reading/show_readings_for_state”, :with =>
“‘state_id=’+this.value+'”) } %>

This collection select will trigger an AJAX call to your
ReadingsController
class for a action named - “show_readings_for_state” which you should
define
in the controller as,

def show_readings_for_state
@readings = Reading.find_all_by_state_id(params[:state_id])
respond_to do |format|
format.js # this will not redirect the page but will look for
javascript template named (“show_readings_for_state.rjs” inside the
folder
“/app/views/readings/”) to execute once #@readings variable is
initialized.
end #End of respond_to do block
end #End of action show_readings_for_state

Now you will need a partial file to replace old list of readings

say _readings_list.html.erb inside
“app/views/readings/_readings_list.html.erb”

And finally the rjs template which will be automatically called after
variables in show_readings_for_state action are initialized…
File could be - “show_readings_for_state.rjs” inside the folder
“/app/views/readings/”

page.replace_html :reading_list_div, :partial=>‘readings_list’ ,
:object=>@readings
page.visual_effect :highlight, ‘reading_list_div’

Maybe this will help you.

Nitin.

veena · March 3, 2010, 11:50am

Hai nitin,

What you think is correct.Now i am getting alllocations irrespective of
state selected pre-displayed on index page.

I want to display only those “districts” which are part of SELECTED
state in collection_select after AJAX operation
Please help me…

Thanks in advance

Veena

veena · March 4, 2010, 7:44am

Veena J. wrote:

Thank u Nithin for your detailed explanation…
But i am still not able to do the ajax functionality…

I hav added <%= javascript_include_tag :defaults %> in my “admin” layout

Controller :

class ReadingsController < ApplicationController
layout “admin”

def index
@time=Time.now
@locations= Station.find(:all,:group => “state”,:order =>“state”)
@district=Station.find(:all)
@readings= CurrentReading.find(:all)
@range=ConfigureParameter.find(:all)
end

end

Hi,
If you are using jquery,you can see e.g
which is similar

veena · March 8, 2010, 8:13am

Now we are talking about ReadingsController index action with a list
of
all locations displayed on it in a div with id say - < div
id=“reading_list_div” >
You need one more action which will be take one argument as selected
state
and will populate a new list of locations which are related to THAT
PARTICULAR state and render the new list of locations via AJAX on the
same
index page.

How can we do this in the controller?I followed all your steps…but in
vain…
Plz reply me

Thanks ,
Veena

veena · March 4, 2010, 6:59am

Thank u Nithin for your detailed explanation…
But i am still not able to do the ajax functionality…

I hav added <%= javascript_include_tag :defaults %> in my “admin” layout

Controller :

class ReadingsController < ApplicationController
layout “admin”

def index
@time=Time.now
@locations= Station.find(:all,:group => “state”,:order =>“state”)
@district=Station.find(:all)
@readings= CurrentReading.find(:all)
@range=ConfigureParameter.find(:all)
end

def show_readings_for_state
@district = Station.find_all_by_state_id(params[:state_id])
respond_to do |format|
format.js
end
end
end

readings/index.html.erb

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

<%= f.label :Stations %>

<%= f.collection_select(:state, @locations, :id, :state,{},{:onclick
=>remote_function(:url =>"/readings/show_readings_for_state",:with
=>"‘state_id=’+this.value+’")} ) %>

<% for sensor_type in @range %> <% end %>

<% for loc in @district %>

<%end%>

Stations	Time Stamp	<%= sensor_type.Parameters %>
<%=f.radio_button :contact_preference, "0", :tabindex =>loc.id %> <%=h loc.district %>

<%end%>

show_readings_for_state.rjs

page.replace_html :reading_list_div, :partial=>‘readings_list’ ,
:object=>@district
page.visual_effect :highlight, ‘reading_list_div’

_readings_list.html.erb

<% for loc in @district %>
<%= radio_button :contact_preference, “0”, :tabindex =>loc.id %>
<%=h loc.district %>

 <%end%>

This is the code.please look at it and help me.

Thank you,
Veena

veena · March 8, 2010, 8:59am

Do one thing, give me migrations or the sql dump of your database
structure,
and your app’s directory zip, I will try to replicate the issues you’re
having and then can assist you further. Because “not able to do the ajax
functionality” is a very big scope of a problem, there can be many
reasons.

veena · March 8, 2010, 10:24am

Your routes file is missing. And on which page do you need the
functionality
working… ?
(without css it is looking all black and white)
Nitin…

veena · March 8, 2010, 9:33am

Hai Nitin,

I am sending you the app and migrations folder.Please have a look.I

know that i am asking too many questions…Sorry 4 troubling you…

Thank you very much…

Veena

veena · March 8, 2010, 10:30am

Veena J. wrote:

Nitin Rajora wrote:

Your routes file is missing. And on which page do you need the
functionality
working… ?
(without css it is looking all black and white)
Nitin…

I want the things to be working on the readings/index

veena · March 8, 2010, 2:22pm

Hi Veena,

I wasn’t sure what was the Data you wanted to display on your Readings
index
page, but I have assumed following situation…

Readings table initially is showing all current_readings for all
stations
on index page
There is a stations dropdown filled with all the stations inside
“stations” table.
When user selects a particular station from the dropdown, the table
showing Readings… should be updated for current_readings specific to
selected station…

I have added some entries to current_readings table.

Have a look, And AJAX is supposed to work on Readings/index page.
I have also added a route in your routes file.

Hope you can change this working AJAX structure according to your
requirements

I am attaching two files -

Zip of the dummy app I created to make AJAX work.
sql for the database I used.
Nitin

veena · March 9, 2010, 5:43am

Thanku Thanku Thanku soooooooo much…You have really helped me a
lot…
The thing you assumed is right for some extend.

Readings table initially is showing all current_readings for all
stations
on index page
There is a stations dropdown filled with all the states in the
“stations” table.(eg.,Karnataka,Mumbai etc)

3.When user selects a particular state from the dropdown, the table
showing Readings… should be updated for current_readings specific to
selected state…(eg. If i select “karnataka” and i hav 2 stations in
Karnataka it should update the readings of those two stations for
current_readings)

Your explanations are very easy to understand…Thank you sooooooooo
much.

Thanks,
Veena

veena · March 8, 2010, 10:29am

Nitin Rajora wrote:

Your routes file is missing. And on which page do you need the
functionality
working… ?
(without css it is looking all black and white)
Nitin…

Hai Nitin,

I have attached the css and the config directory

Thanks,
Veena

veena · March 9, 2010, 5:55am

Sincerely, glad you made it work.
Nitin.

veena · March 9, 2010, 10:50am

Hi Veena,

It is simple logic… Instead of finding CurrentReadings by station_id,
you
need to find CurrentReadings for stations_id for which
stations.state==SELECTED_STATE_VALUE

Files are attached have a look.

Nitin.

veena · March 9, 2010, 9:52am

Hai Nitin,

I am again disturbing you.....Your code is working fine for me.But i

want something like this.

Readings table initially is showing all current_readings for all
stations
on index page
There is a stations dropdown filled with all the states in the
“stations” table.(eg.,Karnataka,Mumbai etc)

3.When user selects a particular state from the dropdown, the table
showing Readings… should be updated for current_readings specific to
selected state…(eg. If i select “karnataka” and i hav 2 stations in
Karnataka it should update the readings of those two stations for
current_readings)

When i got your code i thought i can make the change very easily.I
wasted this whole morning in doing this.I don’t know where i am going
wrong.

Can you please help me out…

Thanks,
Veena

veena · March 9, 2010, 11:27am

Thank you sooooooooooooooooo much…

I was stuck with some syntax error.

Thanks Once Again…

Sincerely,
Veena

veena · March 9, 2010, 11:59am

Hai Nitin,

You have helped me a lot......

Can you please suggest me some good books or links where a newbie like
me can understand Ruby on rails much better…

Thank you once again…

Sincerely,
Veena