No method error rails - ruby-on-rails

Question

please try to understand my question:
when i shut down the webrick server and again restart it ,then in my index view file there are some records after starting server if i click on any of three option (show,edit,delete)it gives me error "undefined method id' for nil:NilClass" and for "show" option "undefined methodname' for nil:NilC"
but if i add new record then every thing works fine i dont know what is the error
this is delete file
<%= link_to("<< Back to List", {:action => 'index'}, :class => 'back-link') %>
<div>
<h2>Delete vendor</h2>
<%= form_for(:vendor, url: {action:'destroy', id: #vendor.id}) do |f| %>
<p>Are you sure you want to permanently delete this vendor?</p>
<p><%= #vendor.name %></p>
<div>
<%= submit_tag("Delete vendor") %>
</div>
<% end %>
</div>
and this is controller
class VendorController < ApplicationController
def index
#vendors=Vendor.all
end
def new
#initiate new vendor which hits back to create
#vendor=Vendor.new
end
def create
#vendor=Vendor.new(vendor_params)
if#vendor.save
flash[:notice]="vendor ceated"
redirect_to(action: 'index')
else
flash[:notice]="there is error"
render('new')
end
def show
#vendor=Vendor.find(params[:id])
end
def edit
#vendor=Vendor.find(params[:id])
end
def update
#vendor=Vendor.find(params[:id])
if #vendor.update_attributes(vendor_params)
flash[:notice]='record updated'
redirect_to(action:'index')
else
flash[:notice]='there is some error'
render('edit')
end
end
def delete
#vendor=Vendor.find(params[:id])
end
def destroy
#vendor=Vendor.find(params[:id]).destroy
if #vendor.destroy
redirect_to(action: 'index')
else
render('delete')
end
end
end
private
def vendor_params
params.require(:vendor).permit(:name ,:image_url)
end
end
this is edit
<%= link_to("<< Back to List", {:action => 'index'}) %>
<div>
<h2>update Vendor</h2>
<%= form_for(:vendor, :url => {:action => 'update', id: #vendor.id }) do |f| %>
<%= render(partial:"form" , locals: {f: f}) %>
<div class="form-buttons">
<%= submit_tag("Update vendor") %>
</div>
<% end %>
</div>
this is show
<%= link_to("<<BAck to main",{action:"index"}) %>
<div>
<h1>showing <%=#vendor.name %></h1>
<p><%=#vendor.image_url %></p>
</div>

Answer 1

Good to see you fixed the problem.
--
For the benefit of future visitors, the error was caused by your controller name being singular, rather than plural.
All controllers should be named in the plural; all models in the singular:
#app/models/vendor.rb
class Vendor < ActiveRecord::Base
end
#app/controllers/vendors_controller.rb
class VendorsController < ApplicationController
end
As an added recommendation, your forms could be tidied up considerably by using the #vendor variable:
#app/views/vendors/edit.html.erb
<%= form_for #vendor do |f| %>
This will auto-fill the path and method, depending on the construct of the object you've passed.