What the title says. I've been trying to google it, but it's a little difficult to phrase it so google knows what I'm looking for (especially since I don't know the terminology).
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1It's called a "hashrocket": http://stackoverflow.com/questions/4663074/in-ruby-what-does-mean-and-how-does-it-work – August Dec 29 '14 at 22:54
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:this => :that is called hashrockets and are superior in every way... – John Naegle Dec 29 '14 at 22:55
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Thanks for the answer! But this post doesn't seem to explain the difference between hashrockets and the other syntax. – Raynor Kuang Dec 29 '14 at 22:56
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When the key: value syntax is used in a Hash literal, the key always becomes a Symbol:
{foo: "bar"}.keys[0].class # => Symbol
When the key => value syntax is used, the key can be any type (including a Symbol):
{:foo => "bar"}.keys[0].class # => Symbol
{1 => "bar"}.keys[0].class # => Fixnum
August
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The "hashrocket" syntax => is used to match up any key value pair in a hash. The newer (and shorter) syntax for hash key value pairs : can only be used for symbol keys.
{foo: bar}
is equivalent to:
{:foo => bar}
Generally speaking if all the keys in your hash are (or should be) symbols then I would recommend the new syntax as it is shorter and reads more easily
{a: 1, b: 2}
However, if any of the keys are not symbols then I would recommend using the older, more flexible syntax:
{"what" => 3, :frequency => 4.43, kenneth => "Bob"}
Coenwulf
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this: value is the newer syntax for hash literals from ruby 1.9.3 onwards.
:this => value is the older syntax; and is valid in newer versions of ruby as well.
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Prakash Murthy
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