How to redirect to a 404 in Rails

Question

I d like to  fake  a 404 page in Rails  In PHP  I would just send a header with the error code as such   header  HTTP 1 0 404 Not Found      How is that done with Rails

User · Answer

Raising ActionController  RoutingError  not found   has always felt a little bit strange to me - in the case of an unauthenticated user  this error does not reflect reality - the route was found  the user is just not authenticated  I happened across config action dispatch rescue responses and I think in some cases this is a more elegant solution to the stated problem    application rb config action dispatch rescue responses        UnauthenticatedError    gt   not found      my controller rb before action  verify user authentication  def verify user authentication   raise UnauthenticatedError if  user authenticated  end  What s nice about this approach is   It hooks into the existing error handling middleware like a normal ActionController  RoutingError  but you get a more meaningful error message in dev environments It will correctly set the status to whatever you specify in the rescue responses hash  in this case 404 - not found  You don t have to write a not found method that needs to be available everywhere

User · Answer

The selected answer doesn t work in Rails 3 1  as the error handler was moved to a middleware  see github issue    Here s the solution I found which I m pretty happy with   In ApplicationController     unless Rails application config consider all requests local     rescue from Exception  with   handle exception   end    def not found     raise ActionController  RoutingError new  Not Found     end    def handle exception exception nil      if exception       logger   Logger new STDOUT        logger debug  Exception Message    exception message   n        logger debug  Exception Class    exception class   n        logger debug  Exception Backtrace   n        logger debug exception backtrace join   n         if  ActionController  RoutingError  ActionController  UnknownController  ActionController  UnknownAction  include  exception class          return render 404       else         return render 500       end     end   end    def render 404     respond to do  format        format html   render template   errors not found   layout   layouts application   status  404         format all   render nothing  true  status  404       end   end    def render 500     respond to do  format        format html   render template   errors internal server error   layout   layouts application   status  500         format all   render nothing  true  status  500      end   end   and in application rb   config after initialize do  app    app routes append  match   a    to   gt   application not found    unless config consider all requests local end   And in my resources  show  edit  update  delete     resource   Resource find params  id   or not found   This could certainly be improved  but at least  I have different views for not found and internal error without overriding core Rails functions

User · Answer

HTTP 404 Status  To return a 404 header  just use the  status option for the render method   def action     here the code    render  status   gt  404 end   If you want to render the standard 404 page you can extract the feature in a method   def render 404   respond to do  format      format html   render  file   gt     Rails root  public 404    layout   gt  false   status   gt   not found       format xml    head  not found       format any    head  not found     end end   and call it in your action  def action     here the code    render 404 end   If you want the action to render the error page and stop  simply use a return statement   def action   render 404 and return if params  something  blank       here the code that will never be executed end   ActiveRecord and HTTP 404  Also remember that Rails rescues some ActiveRecord errors  such as the ActiveRecord  RecordNotFound displaying the 404 error page   It means you don t need to rescue this action yourself  def show   user   User find params  id   end   User find raises an ActiveRecord  RecordNotFound when the user doesn t exist  This is a very powerful feature  Look at the following code  def show   user   User find by email params  email   or raise  not found            end   You can simplify it by delegating to Rails the check  Simply use the bang version   def show   user   User find by email  params  email            end

User · Answer

I wanted to throw a  normal  404 for any logged in user that isn t an admin  so I ended up writing something like this in Rails 5   class AdminController  lt  ApplicationController   before action  blackhole admin    private    def blackhole admin     return if current user admin       raise ActionController  RoutingError   Not Found    rescue ActionController  RoutingError     render file     Rails root  public 404   layout  false  status   not found   end end

User · Answer

these will help you     Application Controller     class ApplicationController  lt  ActionController  Base   protect from forgery   unless Rails application config consider all requests local                  rescue from ActionController  RoutingError  ActionController  UnknownController    AbstractController  ActionNotFound  ActiveRecord  RecordNotFound  with  lambda    exception  render error 404  exception     end    private     def render error status  exception        Rails logger error status to s         exception message to s       Rails logger error exception backtrace join   n          respond to do  format          format html   render template   errors error   status   status  status           format all   render nothing  true  status  status         end     end end   Errors controller  class ErrorsController  lt  ApplicationController   def error 404      not found path   params  not found    end end   views errors error 404 html haml   site    services-page       error-template        h1         Oops         h2         404 Not Found        error-details         Sorry  an error has occured  Requested page not found          You tried to access     not found path    which is not a valid page         error-actions          a button simple orange btn btn-primary btn-lg href  root path             span glyphicon glyphicon-home           Take Me Home

User · Answer

To test the error handling  you can do something like this   feature ErrorHandling do   before do     Rails application config consider all requests local   false     Rails application config action dispatch show exceptions   true   end    scenario  renders not found template  do     visit   blah      expect page  to have content  The page you were looking for doesn t exist     end end

User · Answer

routes rb   get   unmatched route   to   main not found   main controller rb   def not found     render  file   gt     Rails root  public 404 html    status   gt  404   layout   gt  false   end

User · Answer

You could also use the render file   render file     Rails root  public 404 html   layout  false  status  404   Where you can choose to use the layout or not   Another option is to use the Exceptions to control it   raise ActiveRecord  RecordNotFound   Record not found

User · Answer

The newly Selected answer submitted by Steven Soroka is close  but not complete   The test itself hides the fact that this is not returning a true 404 - it s returning a status of 200 -  success    The original answer was closer  but attempted to render the layout as if no failure had occurred   This fixes everything   render  text   gt   Not Found    status   gt   404    Here s a typical test set of mine for something I expect to return 404  using RSpec and Shoulda matchers   describe  user view  do   before do     get  show   id   gt   nonsense    end    it   should not assign to  user      it   should respond with  not found     it   should respond with content type  html      it   should not render template  show     it   should not render with layout      it   should not set the flash   end   This healthy paranoia allowed me to spot the content-type mismatch when everything else looked peachy    I check for all these elements  assigned variables  response code  response content type  template rendered  layout rendered  flash messages   I ll skip the content type check on applications that are strictly html   sometimes  After all   a skeptic checks ALL the drawers      http   dilbert com strips comic 1998-01-20   FYI  I don t recommend testing for things that are happening in the controller  ie  should raise   What you care about is the output   My tests above allowed me to try various solutions  and the tests remain the same whether the solution is raising an exception  special rendering  etc

User · Answer

Don t render 404 yourself  there s no reason to  Rails has this functionality built in already  If you want to show a 404 page  create a render 404 method  or not found as I called it  in ApplicationController like this    def not found   raise ActionController  RoutingError new  Not Found   end   Rails also handles AbstractController  ActionNotFound  and ActiveRecord  RecordNotFound the same way   This does two things better    1  It uses Rails  built in rescue from handler to render the 404 page  and 2  it interrupts the execution of your code  letting you do nice things like     user   User find by email params  email   or not found   user do something    without having to write ugly conditional statements   As a bonus  it s also super easy to handle in tests   For example  in an rspec integration test     RSpec 1  lambda     visit   something you want to 404    should raise error ActionController  RoutingError     RSpec 2   expect     get   something you want to 404    to raise error ActionController  RoutingError    And minitest   assert raises ActionController  RoutingError  do    get   something you want to 404  end   OR refer more info from Rails render 404 not found from a controller action

User · Answer

lt    render file   public 404   status  404  formats    html    gt    just add this to the page you want to render to the 404 error page and you are done

User · Answer

If you want to handle different 404s in different ways  consider catching them in your controllers  This will allow you to do things like tracking the number of 404s generated by different user groups  have support interact with users to find out what went wrong   what part of the user experience might need tweaking  do A B testing  etc   I have here placed the base logic in ApplicationController  but it can also be placed in more specific controllers  to have special logic only for one controller   The reason I am using an if with ENV  RESCUE 404    is so I can test the raising of AR  RecordNotFound in isolation  In tests  I can set this ENV var to false  and my rescue from would not fire  This way I can test the raising separate from the conditional 404 logic   class ApplicationController  lt  ActionController  Base    rescue from ActiveRecord  RecordNotFound  with   conditional 404 redirect if ENV  RESCUE 404    private    def conditional 404 redirect     track 404  current user      if  current user present        redirect to user home               else       redirect to front     end   end  end

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