With the release of the fourth episode of the Rails saga, this is a very exiting time to be a Rails developer.
Even though the beta is not out yet, there are already a few resources available on the Internet for those who want to know more, but this information is still not well known and scattered across the Internet.
Here is a quick list of the best articles and videos available at the moment, with a quick explanation of some of the most interesting features coming in Rails 4.
Aaron Patterson describes, with his funny style, thread safety and improved http streaming in Rails 4. This is a good start to know more about the refactoring that has been done in Rails 4 around thread safety, and understand better what that means.
This is a fantastic quick introduction to what's new and what's deprecated in the new Rails by Andy Lindema from Highgroove Studio.
These are the main features that Andy mentions in the presentation:
A new API for queuing.
A better way to deal with mass assignment problems by filtering parameters in the controller rather than the model. This functionality is already available in the strong_parameters gem that can be used on existing applications.
Turned on by default, this functionality turns each link into an ajax call that will extract the content inside thetags from the response and replace it into the current DOM. Yehuda Katz has some concerns about Turbolinks that he describes in this post, whereas Steve Klabnik posts some interesting numbers.
Caching on Rails just got awesome. The caching strategy used in Basecamp and detailed in this post has been brought into Rails. I'm looking forward to try this on a real application. More info https://github.com/rails/cache_digests
Ability to send partial responses to the client immediately. If you are interested in knowing more checkout Aaron Patterson's "Is it Live?" blog post or Why Rails 4 Live Streaming is a big deal by Hongli Lai on.
For HTML purists the new default HTTP verb used for updates is PATCH. Github issue.
Ruby >= 1.9.3 is now required. Also traditional plugins are gone forever.
Prem Sichanugrist gave also a very good talk at Boston RB.
Hope you found this list of resources useful. I will try to keep this list up to date in the next few weeks so come back regularly. Let me know in the comments if I missed some interesting link or article.