How do i access an id from the link?

I am displaying list of cities from the database ,each as a link.I want when a user click on any of the cities ,the action respond by grabbng the id of that city and re use it on the next action(show action in this case).So How do you grab an id from the link?Below is my idea which didnt work.Thank you in advance.

View/cities

    <%@cities.each do |city| %>
    <a href="/deal/city"><%=city.name%></a><br/>
    <%end%>

Controller

   Class DealController < ApplicationController
   def all_cities
   @cities=City.find(:all)
   end

   def city
   @city=City.find(params[:city_id]) 
   session[:city_id] = @city.id
   redirect_to :controller=>"deal",:action=>"show"
   end  

   def show
   unless session[:city_id].nil? || 开发者_StackOverflowsession[:city_id].blank?
   @city = City.find(session[:city_id])
   @deals=@city.deals
   end

   end

routes

    get "deal/city"
    match 'deal/city'  => "deal#city"

You are not passing the city_id in the link. Try:

<% @cities.each do |city| %>
    <a href="/deal/city?city_id=<%= city.id %>"><%= city.name %></a><br/>
<% end %>

If you want the link to be like "/deal/city/1" and get 1 as params[:city_id], you can modify your routes like this:

match 'deal/city/:city_id'  => "deal#city", :via => :get

and use the link like this:

<% @cities.each do |city| %>
    <a href="/deal/city/<%= city.id %>"><%= city.name %></a><br/>
<% end %>