Else part is not working in Rails ajax form - ruby

Question

I have a Rails ajax form to submit.When user will give the correct data it will search the database and do the operation accordingly.If user is giving the Wrong data it should display user to alert message.But it is not happening like that.
I am explaining my codes below.
home.html.erb
<% if current_admin %>
<p class="flash-message"><%=flash[:notice]%></p>
<div class="col-md-6" style="float:none; margin:auto;">
<%= form_for :sdf ,:url => {:action => "scan_report" },remote: true do |f| %>
<% if params[:receipt_no] %>
<div class="input-group bmargindiv1 col-md-12"> <span class="input-group-addon text-left">Receipt No. Scan :</span>
<%= f.text_field :Receipt_No,:class => "form-control", :value => params[:receipt_no] %><%= f.submit "Scan Report" %>
</div>
<% else %>
<div class="input-group bmargindiv1 col-md-12"> <span class="input-group-addon text-left">Receipt No. Scan :</span>
<%= f.text_field :Receipt_No,:class => "form-control",placeholder:"Receipt No. scan" %><%= f.submit "Scan Report" %>
</div>
<% end %>
<% end %>
<% end %>
controller/homes_contorller.rb
class HomesController < ApplicationController
def home
#sdf=TSdf.new
respond_to do |format|
format.html
format.js
end
end
def scan_report
if #sdf=TSdf.find_by_Receipt_No(params[:sdf][:Receipt_No])
if #sdf && #sdf.HCSY_Status=='YES'
#hcsy=THcsy.find_by_Sdp_Id(#sdf.Sdp_Id)
#hcsy_deatils=THcsyDetails.find_by_HCSY_ID(#hcsy.id)
#woods=THcsyFundTypeMaster.find_by_Fund_Type_Code(1)
#burn=THcsyFundTypeMaster.find_by_Fund_Type_Code(2)
#good=THcsyFundTypeMaster.find_by_Fund_Type_Code(3)
#swd=THcsyFundTypeMaster.find_by_Fund_Type_Code(5)
#photo=THcsyFundTypeMaster.find_by_Fund_Type_Code(6)
end
else
flash[:notice]="Not Found"
end
end
end
In this form its only taking the correct input but if user is trying to give the wrong input the else part is not executing.Please help me to resolve this error and let me to know how can i make this ajax call in below format.
$('form').submit(function() {
var valuesToSubmit = $(this).serialize();
$.ajax({
type: "POST",
url: $(this).attr('action'), //sumbits it to the given url of the form
data: valuesToSubmit,
dataType: "JSON" // you want a difference between normal and ajax-calls, and json is standard
}).success(function(json){
console.log("success", json);
});
return false; // prevents normal behaviour
});
Please help me.I am using Rails version 3.2.19.

Answer 1

Here you send AJAX POST request to scan_report, and if it is successful it should render template scan_report.js.erb, and rendered template will appear in json variable in success callback.
But if params are not valid, the same template is rendered, but all instance variables are missing. And probably empty json is returned or an error appears in log.
Anyway, if you'd like to change flash in remote form, you should put custom code in fail callback. Something like
$("#flash").html('<%= j render flash[:notice] %>');