Question

What does this do in Rails?

create! do |user| 
  #initialise user 
end

I figured it creates a user objects and saves it to the database. How is it different from just saying user.new(...) and user.save()?

Answer 1

In a nutshell:

• create! raises an exception while create returns the object (unsaved object if it does not pass validations).
• save! raises an error while save returns true/false.
• save does not take attributes, create does.

new does not save. new is similar to build in ActiveRecord context.
create saves to the database and returns true or false depending on model validations.
create! saves to the database but raises an exception if there are errors in model validations (or any other error).