What does the ampersand at the end of a Ruby parameter mean?

Question

Below is an example of named arguments in Ruby, but what does the ampersand do?

def set_tools(foo:, bar:, baz:)
    @instance_variable = baz&.stuff

It's the [Safe Navigation Operator](http://mitrev.net/ruby/2015/11/13/the-operator-in-ruby/). It made its debut in Ruby 2.3. — Cary Swoveland, Aug 02 '17 at 06:58
See this https://stackoverflow.com/questions/36812647/what-does-ampersand-dot-mean-in-ruby — Rajkaran Mishra, Aug 02 '17 at 06:58

score 8 · Answer 1 · answered Aug 02 '17 at 06:58

It is called as Safe Navigation Operator. Introduced in ruby 2.3.0

You can use it to make sure the value exist before calling some method on it

For example:

a = nil

a.some_method # This will break

#=> NoMethodError: undefined method `some_method' for nil:NilClass

a&.some_method # This will not

#=> nil

You can use this operator instead of

a && a.some_method && a.some_method.some_other_method
# OR
a.try(:some_method).try(:some_other_method)

Using this operator

a&.some_method&.some_other_method

1 Answers1