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In this example, you ll use before_filter to perform some logic before every request to the application. To do this, you ll add some code to app/controllers/application_controller.rb so that every controller in your application (although there is only one in this case, entries) will be subjected to the filter. Here s app/controllers/application_controller.rb before the new code: # Filters added to this controller will be run for all controllers in the # application. # Likewise, all the methods added will be available for all controllers. class ApplicationController < ActionController::Base helper :all # include all helpers, all the time protect_from_forgery # See ActionController::RequestForgeryProtection

Notice how we re able to selectively apply the filter to specific actions. Here, we want every action to be protected except for index and show. The :except modifier accepts either a single value or an array. We re using an array here. If you want to protect only a few actions, you can use the :only modifier, which, as you would expect, behaves the opposite of :except. We also want to use a filter in the users controller. Right now, anyone can edit a user as long as they know the user ID. This would be risky in the real world. Ideally, we want the edit and update actions to respond only to the currently logged-in user, allowing that user to edit his profile. To do this, instead of retrieving User.find(params[:id]), we ll retrieve the current_user and apply a filter to protect the edit and update actions. Listing 6-23 shows the latest version of the users controller, the updated code is highlighted in bold.

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In the blog application, you d like to make sure no one creates a comment for an article that hasn t been published yet. First, you need to create a method so you can ask an Article if its published_at field is null or not by using the present method which returns true if a values exists, and false otherwise. This method is useful outside validations, because you may want to indicate on the administration interface later whether an article has been published. Let s add that method now and call it published . Add the code shown in Listing 5-28 to the Article model.

class UsersController < ApplicationController before_filter :authenticate, :only => [:edit, :update] def show @user = User.find(params[:id]) end def new @user = User.new end def create @user = User.new(params[:user]) if @user.save flash[:notice] = 'Thanks for signing up!' redirect_to :controller => 'events', :action => 'index' else render :action => 'new' end end def edit @user = current_user end def update @user = current_user if current_user.update_attributes(params[:user]) flash[:notice] = 'Information updated' redirect_to :action => 'show', :id => current_user.id else render :action => 'edit' end end def login if request.post if user = User.authenticate(params[:login], params[:password]) session[:user_id] = user.id redirect_to :controller => 'events', :action => 'index'

Pay attention to the comments left in default files, as they are often quite informative, as in the Tip preceding code.

Here s the same file after implementing your request-counting code (and removing the comments): class ApplicationController < ActionController::Base helper :all protect_from_forgery before_filter :count_requests_in_session def count_requests_in_session session[:requests] ||= 0 session[:requests] += 1 end end You use before_filter with a symbol as a parameter, where the symbol represents the count_requests_in_session method.

else flash[:notice] = 'Invalid login/password combination' end end end def logout session[:user_id] = nil redirect_to :action => 'login' end end

Within the count_requests_in_session method, a hash provided by Rails called session is used. Automatically, session is always a data store associated with the current session, so anything you write to it or read from it is always associated with the current session. In this case, you initialize session[:requests] with 0 if it not already defined, and then you increase the count on the next line. You can access this information from your views now quite easily. Go to app/views/entries/view_all.html.erb and add this line to the top of the file: <%= session[:requests] %> If you now load http://localhost/entries/view_all (or just http://localhost/ if you followed the Routing section earlier), you ll see 1 at the top of the page. Reload the page, and the number increases for each reload. Sessions in action!