TIL, 2017-03-15, AR Merge

Apparently active_model.errors.full_messages exists, and is not something like active_model.errors.map { |x| x.full_messages }.
rescue block implicitly begins in a method’s scope. If you want to rescue while inside a method to rescue at any time inside a method, then just put rescue, no need to do begin.
each_with_object is better than inject because of the chances to do bugs.
You can use adapter classes to convert AR models to service class value objects.
AR merge is about 10x faster than a map after the initial query is done link.
The head, *tail and required_options, **optional_options (hehe) is very useful!
You can do this: obj.methods.grep(/my/) to check if methods exist.
ThisTypeOfWriting is called Pascal case (I think I knew this before).