Add element to an array if it's not there already

I have a Ruby class

class MyClass
  attr_writer :item1, :item2
end

my_array = get_array_of_my_class() #my_array is an array of MyClass
unique_array_of_item1 = []

I want to push MyClass#item1 to unique_array_of_item1, but only if unique_array_of_item1 doesn't contain that item1 yet. There is a simple solution I know: just iterate through my_array and check if unique_array_of_item1 already contains the current item1 or not.

Is there any more efficient solution?

You can use Set instead of Array.