when_to_use_do.rb

# For multi-line blocks, use do. E.g.:

users.each do |user|
  user.name = "foo"
  user.save
end

# For single-line blocks, use {} 
users.each {|user| user.destroy }

# Even more trickery (equivalent to one above):
users.each(&:destroy)

# EXCEPTION: multi-line blocks, that are called by something else Example:
users.map { |user|
  user.name  
}.join("\n") 

# This is equivalent, but looks strange
users.map do |user|
  user.anem
end.join("\n")