class Hash
  # Returns a hash with non +nil+ values.
  #
  #   hash = { a: true, b: false, c: nil }
  #   hash.compact        # => { a: true, b: false }
  #   hash                # => { a: true, b: false, c: nil }
  #   { c: nil }.compact  # => {}
  #   { c: true }.compact # => { c: true }
  def compact
    select { |_, value| !value.nil? }
  end

  # Replaces current hash with non +nil+ values.
  # Returns nil if no changes were made, otherwise returns the hash.
  #
  #   hash = { a: true, b: false, c: nil }
  #   hash.compact!        # => { a: true, b: false }
  #   hash                 # => { a: true, b: false }
  #   { c: true }.compact! # => nil
  def compact!
    reject! { |_, value| value.nil? }
  end
end