Partial not updated on first click - ruby-on-rails

Question

I am having problems with a remotely executed action and a partial that doesn't update the first time I click the link.
Inside the view (a partial named books) I am creating a link:
link_to "⊗", read_book_path(book), :remote => true
The read_book_path is defined in routes.rb
There is also a conditional that displays a different text when that book is read.
Inside my controller, I have defined a new action:
def read
#books = Book.all
#book = Book.find(params[:id])
#book.read = !#book.read
#book.save
respond_to do |format|
format.html { redirect_to(books_url) }
format.js {render :layout => false, :locals => { :book => #book } }
end
end
This means I need a file read.js.erb, this file's content is:
$("#books").empty().html("<%= escape_javascript( render(:partial => "books") ) %>");
When I click the link, I can see in the terminal window that the database field is updated but the partial is not. Clicking the same link again updates the partial.
Changing the link to :remote => false also works but the page reloads (as expected).
I have tried to debug it with Safari and the Developer tools and I can see the server's response when clicking the link for the first time.
Something is wrong there, the HTML generated by <%= escape_javascript( render(:partial => "books") ) %> contains the wrong HTML with the old content of the partial. Only the second or third click shows the updated HTML.
I have integrated jquery-ujs - is that the reason the partial doesn't update the first time or am I missing something else?
This really gave me a headache, can you help me?
Edit:
If that helps: I created a listener in application.js to ajax:before and ajax:complete. The first one shows a little spinner, the second one hides it.
When I click the link, the spinner shows but it doesn't hide.

Answer 1

It looks like you have an ordering problem that's causing the trouble. You're capturing a complete set of books into the #books variable and then modifying a separate copy of a single book. This change will not be propagated back.
# Load and modify the one book by flipping the flag
#book = Book.find(params[:id])
#book.read = !#book.read
#book.save
# Load all books
#books = Book.all
As a note this is an extremely inefficient way of doing things, so I hope you're not working on a large amount of data. You might find it's easier to do this by simply toggling the one field with a simple UPDATE query:
Book.update_all({ :read => true }, { :id => params[:id] })
I'm not sure why you're calling $(...).empty().html(...) instead of simply $(...).html(...) since the html() method should replace the HTML wholesale with no need to clear it in advance.
One thing that might help is using .js.rjs where the equivalent would be:
page[:books].replace_html(:partial => 'books')
With simple JavaScript, RJS allows you to eliminate a lot of the drudgery. You can use JS in RJS as well for cases where there is no equivalent:
page << '$("#books").empty()'
page[:books].replace_html(:partial => 'books')
To make this more Rails friendly, you could call your partial _book which would make the local variables redundant. Each partial has a default variable with a name matching the template name:
render(:partial => 'book', :collection => #books)