Unable to search queries from database in rails 3 - ruby-on-rails

Question

I am working on rails to search the desired results. I have a table called coordinates, and I want a search form for that my model.rb
class Coordinates<ActiveRecord::Base
attr_accessible :city , :latitude, :longitude
end
coordinates_controller.rb
class CoordinatesController<ApplicationController
def show
#coordinates=Coordinates.where("city = ?", params[:search]).all
end
end
index.html.erb
<%= form_tag({controller: "coordinates", action: "show"}, method: "get") do %>
<%= label_tag(:coordinates,"search for:") %>
<%= text_field_tag(:show) %>
<%= submit_tag("search") %>
<% end %>
search.html.erb
<%= form_for #coordinates.search do |coordinates| %>
<ul>
<li><%= coordinates.latitude %></li>
<li><%= coordinates.longitude %></li>
<li><%= coordinates.longitude %></li>
</ul>
<% end %>
but I am getting this error:
undefined method `search' for []:Array
.. please help

Answer 1

To begin, try changing the form code in index.html.erb from:
<%= form_tag({controller: "coordinates", action: "show"}, method: "get") do %>
<%= label_tag(:coordinates,"search for:") %>
<%= text_field_tag(:show) %>
<%= submit_tag("search") %>
<% end %>
To:
<%= form_tag({controller: "coordinates", action: "show"}, method: "get") do %>
<%= label_tag(:search,"search for:") %>
<%= text_field_tag(:search) %>
<%= submit_tag("Search") %>
<% end %>
This will populate params[:search] with the value of the text field. Currently you are passing your query as params[:show].
Next, try changing your search results view to:
<% #coordinates.each do |coordinates| %>
<ul>
<li><%= coordinates.latitude %></li>
<li><%= coordinates.longitude %></li>
<li><%= coordinates.longitude %></li>
</ul>
<% end %>
This iterates over the #coordinates collection returned by your controller.

Answer 2

From the line
undefined method 'each' in nil:Nilclass
It seems that there are no coordinates for the city you looking for in your database
after the call
#coordinates=Coordinates.where("city = ?", params[:search]).all
check #coordinates.nil? and #coordinates.count to see if this is the case
And beside it is a better practice to check it before using it - so you can handle it in the way you want - in case that something went wrong in your DB and you don't want the user to get such errors on production