Example of ruby contracts

kit-contracts.rb

module RGB

  # First step -----------------------------------------------------------------

  before ->(r:, g:, b:) { (0..255) === r && (0..255) === g && (0..255) === b }
  after  [
    ->(result:) { result.is_a?(String) },
    ->(result:) { result.start_with?('#') },
    ->(result:) { result.length.in?([4, 7]) },
  ]
  def self.rgb_to_hex_1a(r:, g:, b:)
    "+" << [r, g, b].map { |el| el.to_s(16) }.join
  end

  # Or

  contracts_attributes = {
    before: ->(r:, g:, b:) { (0..255) === r && (0..255) === g && (0..255) === b }
    after:  [
      ->(result:) { result.is_a?(String) },
      ->(result:) { result.start_with?('#') },
      ->(result:) { result.length.in?([4, 7]) },
    ],
  }

  contract contracts_attributes
  def self.rgb_to_hex_1b(r:, g:, b:)
    "+" << [r, g, b].map { |el| el.to_s(16) }.join
  end


  # Second step ----------------------------------------------------------------

  RgbType = Types::Int.values(0..255)

  before { r: RgbType, g: RgbType, b: RgbType, }
  after  [
    Types::String,
    ->(result:) { result.start_with?('#') },
    ->(result:) { result.length.in?([4, 7]) },
  ]
  def self.rgb_to_hex2(r:, g:, b:)
    "+" << [r, g, b].map { |el| el.to_s(16) }.join
  end

end