Enter Subdomain name inside input field and redirect to its domain if the subdomain present.

controller.rb

def proceed
  	@domain_from_form = params[:search][:q] 
  	@domain_search = User.pluck(:subdomain)
 	@domain_present = @domain_search.include? @domain_from_form
	if @domain_present == true
  		redirect_to "http://#{@domain_from_form}.lvh.me:3000/accounts/sign_in"
  	else
		redirect_to resub_index_path
  	end
  end

form.html.erb

<h1>Enter the Subdomain</h1>
<%= form_for :search, :url => { :method => :get, :action => :proceed } do |f| %>
  <%= f.label :q, "Enter the Subdomain" %>
  <%= f.text_field  :q %>
  <%= f.submit "Proceed" %>
<% end %>