Deduping an array in Ruby using the uniq method is simple.

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["a", "a", "b", "b", "c"].uniq   #=> ["a", "b", "c"]

Deduping an array of objects based on a specific attibute can be more complicated.

Rails includes a uniq_by method.

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[1, 2, 3, 4].uniq_by { |i| i.odd? } # => [1, 2]

If you are working without Rails, the Hash works nicely since it allows only one instance of each key.

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a = [1, 2, 3, 4]
Hash[*a.reverse.map{|i|[i.odd?,i]}.flatten].values # => [1, 2]