What is this format in ruby?

In a book they showed me this declaration:

friends = [ { first_name: "Emily", last_name: "Laskin" }, { first_name: "Nick", last_name: "Mauro" }, { first_name: "Mark", last_name: "Maxwell" } ]

This doesn't look like a hash. And when I enter it in IRB i get 开发者_运维百科an error.

What is this format?

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It's an array of hashes, written in the Ruby 1.9 hash syntax.

{ first_name: "Emily", last_name: "Laskin" }

is equivalent to:

{ :first_name => "Emily", :last_name => "Laskin" }

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The {key: value} syntax is new in 1.9 and is equivalent to {:key => value}.

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It is an array of hashes, only the hashes are 1.9 style hashes.