了解jQuery Rails Gem和rails.js

Question

I'm trying to solve the book "Rails 3 in Action" where the authors have used the following code to add a link that uses ajax to generate a new file field. I'm having difficulty in understanding in how this works and what is the equivalent javascript(or jQuery) which can be functionally equivalent to understand it better:

 <%= link_to "Add another file", new_file_path,
     :remote => true,
     :update => "files",
     :position => "after"
 %>

Thanks a lot

Answer 1

Well I'm not sure if we can explain it better than the book. Which part are you having trouble with?

Your code will be turned into an 'a' link, the href for which will be the url for the new_file_path (probably the new method in the file controller). You can examine this path by calling this method in the the rails console by typing app.new_file_path

The 'remote' parameter will cause aa data-remote parameter to the 'a' element with value true, meaning it will be an ajax call. When the page loads rails.js will find the remote parameter and, as a result, bind a click event to an ajax call.

The location to update when the ajax call returns will be the 'files' element on the page.

The position parameter indicates--don't update the files element directly--but put the response in the DOM right after that element.

If that doesn't help try these resources:

http://guides.rubyonrails.org/ajax_on_rails.html

http://net.tutsplus.com/tutorials/javascript-ajax/using-unobtrusive-javascript-and-ajax-with-rails-3/

Answer 2

I'm very confused with that example, because it is incorrect and has nothing to do with Rails 3. Instead authors use somewhat odd syntax from link_to_remote , which is no longer supported in Rails 3.

This helper will generate the link below:

<a update="files" position="after" data-remote="true" href="/files/new">Add another file</a>

which simply fires an AJAX GET request to the /files/new url (because jquery-ujs observes clicks on links with data-remote="true" and produces such requests). It doesn't send any additional params (neither update , nor position ) to a server. The subsequent DOM manipulation is completely up to the response you generate on a server.

Therefore in Rails 3 update and position options is completely useless, if you want to communicate with a server (those may be used in a client side event handler, but it's not that book said about, as I understood).