Rails%203%20In%20Action

240 CHAPTER 9 File uploading
This is a little more verbose than the CoffeeScript and another great demonstration
of how CoffeeScript allows you to write more with less. For more information and
usage examples of CoffeeScript, see the CoffeeScript site: http://coffeescript.org.
Let’s now give your link the id attribute that’s required to get this working so we
can move on.
PASSING THROUGH A NUMBER
Open your app/views/tickets/_form.html.erb and replace the code for your Add
Another File link with this:
"add_another_file" %>
This gives the element the id attribute you require. Let’s witness this JavaScript in
action now by running rails server to start up a server, signing in using the email
address user@ticketee.com and the password password, and then creating a ticket on a
project. Clicking the Add Another File link results in an error that you’ll fix shortly.
Click it anyway. Afterward, go back to the window where rails server is running.
This window shows information such as queries and results for every request, but
you’re only interested in the last request made. This request should begin with the following
line:
Started GET "/files/new?number=1...
This line tells you that Rails has begun serving a GET request to the /files/new route
with a bunch of URL parameters. Your number parameter is the first one in this example.
The following lines show the URL that was requested as well as what action and
controller served this request:
Started GET "/files/new?number=1" for 127.0.0.1 at [timestamps]
Processing by FilesController#new as */*
Parameters: {"number"=>"1"}
The line you’re most interested in is the third line:
Parameters: {"number"=>"1", ... }
This is the params hash output in a semi-human-readable format. Here you can see it
has the number parameter, so you can use this inside the new action. With all this in
mind, you can change how you render the partial in the new action inside Files-
Controller to this:
render :partial => "files/form",
:locals => { :number => params[:number].to_i,
:asset => asset }
You must convert the number parameter to an integer using the to_i method because
it’ll be a String when it comes from params. It needs to be a Fixnum so the partial can
add 1 to it.