Ruby's safe navigation operator (&.)

Ruby’s safe navigation operator (&.) is a nil-safe way to chain operations.

Let’s say we have a User class, and that class can have first_name and last_name attributes:

me = User.new(first_name: "justin")
me.first_name # "justin"
me.first_name.upcase # "JUSTIN"

# We didn't give me a last_name
me.last_name # nil
me.last_name.upcase # NoMethodError: undefined method `upcase' for nil:NilClass

# using safe navigation, there's no error
me.last_name&.upcase # nil

# you could even chain further
me.last_name&.upcase&.downcase # nil

Without safe navigation, we’d need a more-verbose if check to accomplish the same thing:

# same result as me.last_name&.upcase
if me.last_name
  me.last_name.upcase
else
  nil
end

If you’re familiar with Javascript, ruby’s safe navigation works just like javascript’s optional chaining¹.

Note: &. only works when dealing specifically with nil, not false (or any other falsy value):

me.last_name = false
me.last_name&.upcase # NoMethodError: undefined method `upcase' for false:FalseClass

Javascript’s optional chaining actually handles two different falsey values, null and undefined ↩︎