How do I sort a Ruby array of strings by length?

How do开发者_StackOverflow中文版 I sort this:

arr = ["aaa","aa","aaaa","a","aaaaa"];

Into this?

arr = ["a","aa","aaa","aaaa","aaaaa"];

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arr = arr.sort_by {|x| x.length}

Or in 1.8.7+:

arr = arr.sort_by(&:length)

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You can also use sort:

arr.sort{|x, y| x.length <=> y.length}

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arr = arr.sort{|x,y| x.length - y.length} works too.