Rails 4 is nearly there, we should be ready before it released. Most developers are trying hard to keep their application on the edge.
Must see resources:
1) @sikachu talk:
What to Expect in Rails 4.0 - YouTube
2) Rails Guides release notes: http://edgeguides.rubyonrails.org/4_0_release_notes.html
There is a mix of all major changes down here:
ActionMailer changes excerpt:
Asynchronously send messages via the Rails
Raise an ActionView::MissingTemplate exception when no implicit template could be found
ActionPack changes excerpt
Added controller-level etag additions that will be part of the action etag computation
Add automatic template digests to all CacheHelper#cache calls (originally spiked in the cache_digests plugin)
Add Routing Concerns to declare common routes that can be reused inside others resources and routes
Added ActionController::Live. Mix it in to your controller and you can stream data to the client live
truncate now always returns an escaped HTML-safe string. The option :escape can be used as false to not escape the result
Added ActionDispatch::SSL middleware that when included force all the requests to be under HTTPS protocol
ActiveModel changes excerpt
AM::Validation#validates ability to pass custom exception to :strict option
Changed `AM::Serializers::JSON.include_root_in_json' default value to false. Now, AM Serializers and AR objects have the same default behaviour
Added ActiveModel::Model, a mixin to make Ruby objects work with AP out of box
Trim down Active Model API by removing valid? and errors.full_messages
ActiveRecord changes excerpt
Use native mysqldump command instead of structure_dump method when dumping the database structure to a sql file.
Attribute predicate methods, such as article.title?, will now raise ActiveModel::MissingAttributeError if the attribute being queried for truthiness was not read from the database, instead of just returning false
ActiveRecord::SessionStore has been extracted from Active Record as activerecord-session_store gem. Please read the README.md file on the gem for the usage
Fix reset_counters when there are multiple belongs_to association with the same foreign key and one of them have a counter cache
Raise ArgumentError if list of attributes to change is empty in update_all
Add Relation#load. This method explicitly loads the records and then returns self
Deprecated most of the 'dynamic finder' methods. All dynamic methods except for find_by_... and find_by_...! are deprecated
Added ability to ActiveRecord::Relation#from to accept other ActiveRecord::Relation objects
Remove IdentityMap
ActiveSupport changes excerpt
ERB::Util.html_escape now escapes single quotes
ActiveSupport::Callbacks: deprecate monkey patch of object callbacks
Replace deprecated memcache-client gem with dalli in ActiveSupport::Cache::MemCacheStore
Object#try will now return nil instead of raise a NoMethodError if the receiving object does not implement the method, but you can still get the old behavior by using the new Object#try!
Object#try can't call private methods
Add ActiveSupport::Deprecations.behavior = :silence to completely ignore Rails runtime deprecations
What are the most important changes for you?
