What does &. (ampersand dot) mean in Ruby?

ruby syntax operators parameter-passing ruby-2.3
Sami picture Sami · Apr 23, 2016 · Viewed 36.2k times · Source

I came across this line of ruby code. What does &. mean in this?

@object&.method

Answer

Santhosh picture Santhosh · Apr 23, 2016

It is called the Safe Navigation Operator. Introduced in Ruby 2.3.0, it lets you call methods on objects without worrying that the object may be nil(Avoiding an undefined method for nil:NilClass error), similar to the try method in Rails.

So you can write

@person&.spouse&.name

instead of

@person.spouse.name if @person && @person.spouse

From the Docs:

my_object.my_method

This sends the my_method message to my_object. Any object can be a receiver but depending on the method's visibility sending a message may raise a NoMethodError.

You may use &. to designate a receiver, then my_method is not invoked and the result is nil when the receiver is nil. In that case, the arguments of my_method are not evaluated.

Related questions

What does map(&:name) mean in Ruby?

I found this code in a RailsCast: def tag_names @tag_names || tags.map(&:name).join(' ') end What does the (&:name) in map(&:name) mean?

Read More
What is Ruby's double-colon `::`?

What is this double-colon ::? E.g. Foo::Bar. I found a definition: The :: is a unary operator that allows: constants, instance methods and class methods defined within a class or module, to be accessed from anywhere outside the class or …

Read More
Ruby - test for array

What is the right way to: is_array("something") # => false (or 1) is_array(["something", "else"]) # => true (or > 1) or to get the count of items in it?

Read More