Ruby 1.8: Hash#sort not return hash but array (better way to do this?)

Question

In some scenario of Ruby 1.8. If I have a hash

# k is name, v is order
foo = { "Jim" => 1, "bar" => 1, "joe" => 2}
sorted_by_values = foo.sort {|a, b| a[1] <==> b[1]}
#sorted_by_values is an array of array, it's no longer a hash!
sorted_by_values.keys.join ','

my workaround is to make method to_hash for Array class.

class Array
  def to_hash(&block)
    Hash[*self.collect { |k, v|
      [k, v]
    }.flatten]
  end
end

I can then do the following:

sorted_by_values.to_hash.keys.join ','

Is there a better way to do this?

Noel Walters · Accepted Answer · 2009-01-28 20:36:13Z

3

Hashes are unordered by definition. There can be no such thing as a sorted Hash. Your best bet is probably to extract the keys from the sorted array using collect and then do a join on the result

sortedByValues = foo.sort {|a, b| a[1] <==> b[1]}
sortedByValues.collect { |a| a[0] }.join ','

answered Jan 28, 2009 at 20:36

Noel Walters

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3 Comments

David Phillips Over a year ago

Note that hashes are ordered by key insertion order in Ruby 1.9.

f00860 Over a year ago

Dont rely on the key insertion order in 1.9, this is not a definition, its a implementation feature. If your code works with (Matz)Ruby but not with jRuby, you know what i mean :)

Marc-André Lafortune Over a year ago

@Fu86: No, it's a feature of the language (confirmed by Matz). See intro of Hash's doc: ruby-doc.org/core/classes/Hash.html

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