Value not bind to the view from controller - ruby-on-rails

Question

I have two select tags as follow
<%= f.select(:floor_id, ProjectFloor.find(:all,:order => "name ASC",:conditions => ["project_id = ?", #project.id]).collect{|b|[b.name, b.id]}, {:include_blank => 'Select'}) %>
<%= f.select(:unit_id, #floor.collect{|b|[b.name, b.id]}, {:include_blank => 'Select'}) %>
When the user select the value on the first select tag called :floor_id then the value of the select tag data should be load to :unit_id select tag
I have try the following to read and fetch the data but. the floor_id always receiving null
My controller method is as follow :
#floor_id = params[:floor_id]
#project = Project.find(params[:project_id])
#proposed_customer = ProposedCustomer.new
#floor = ProjectFloorUnit.select_units(#project.id, #floor_id)
The select unit method is work fine for static values so it must work if we pass the proper param.

Answer 1

When a page is completely loaded, it disconnects from the server. So, you need to initiate a separate request, and the response of the request will change the values or whatever you want in the second dropdown.
You can use jQuery to send a new request:
$("#floorIDSelectTag").change(function() {
var floorID = $(this).val();
$.ajax({
type: '',
url: '',
// other things
success: function(data) {
// Here, you need to use the data from the request's response,
// and update the things in 2nd dropdown
}
});
});
What will be the URL that you will use in AJAX call? For it, you need to build a new route in config/routes.rb file, a new action in your controller, and send back the data in JSON format. Something like following:
def get_data_for_floor_id
#floor_id = params[:floor_id]
# Do the other stuff, and prepare the response you need to send.
respond_to do |format|
format.json { }
end
end