How do I check to see if my array includes an object?

Question

I have an array @horses = [] that I fill with some random horses.

How can I check if my @horses array includes a horse that is already incl

Answer 1

So the question is how can I check if my array already has a "horse" included so that I don't fill it with the same horse?

While the answers are concerned with looking through the array to see if a particular string or object exists, that's really going about it wrong, because, as the array gets larger, the search will take longer.

Instead, use either a Hash, or a Set. Both only allow a single instance of a particular element. Set will behave closer to an Array but only allows a single instance. This is a more preemptive approach which avoids duplication because of the nature of the container.

hash = {}
hash['a'] = nil
hash['b'] = nil
hash # => {"a"=>nil, "b"=>nil}
hash['a'] = nil
hash # => {"a"=>nil, "b"=>nil}

require 'set'
ary = [].to_set
ary << 'a'
ary << 'b'
ary # => #
ary << 'a'
ary # => #

Hash uses name/value pairs, which means the values won't be of any real use, but there seems to be a little bit of extra speed using a Hash, based on some tests.

require 'benchmark'
require 'set'

ALPHABET = ('a' .. 'z').to_a
N = 100_000
Benchmark.bm(5) do |x|
  x.report('Hash') { 
    N.times {
      h = {}
      ALPHABET.each { |i|
        h[i] = nil
      }
    }
  }

  x.report('Array') {
    N.times {
      a = Set.new
      ALPHABET.each { |i|
        a << i
      }
    }
  }
end

Which outputs:

            user     system      total        real
Hash    8.140000   0.130000   8.270000 (  8.279462)
Array  10.680000   0.120000  10.800000 ( 10.813385)