Examples of how to avoid the primitive obsession in Ruby.

a_primitive_obsession.rb

rgb = [5, 55, 255]

def rgb_to_hex(r, g, b)
  '#%02x%02x%02x' % [r, g, b]
end

p rgb              # [5, 55, 255]

p rgb_to_hex(*rgb) # "#0537ff"

b_classes.rb

class RGBColor
  Number = ->(value) do
    return value if value.is_a?(Integer) && value.between?(0, 255)

    raise ArgumentError, "given #{value.inspect}, but was expected an integer between 0 and 255"
  end

  attr_reader :red, :green, :blue

  def initialize(r, g, b)
    @red, @green, @blue = Number[r], Number[g], Number[b]
  end

  def to_a
    [red, green, blue]
  end

  def to_hex
    '#%02x%02x%02x' % to_a
  end
end

rgb_color = RGBColor.new(5, 35, 255)

p rgb_color.to_a   # [5, 35, 255]
p rgb_color.to_hex # "#0523ff"

RGBColor.new('a', 1, 255) # ArgumentError: given "a", but was expected an integer between 0 and 255

c_structs.rb

RGBColor = Struct.new(:red, :green, :blue) do
  Number = ->(value) do
    return value if value.is_a?(Integer) && value.between?(0, 255)

    raise ArgumentError, "given #{value.inspect}, but was expected an integer between 0 and 255"
  end

  def initialize(r, g, b)
    super(Number[r], Number[g], Number[b])
  end

  def to_hex
    '#%02x%02x%02x' % to_a
  end
end

rgb_color = RGBColor.new(5, 35, 255)

p rgb_color.to_a   # [5, 35, 255]
p rgb_color.to_hex # "#0523ff"

RGBColor.new('a', 1, 255) # ArgumentError: given "a", but was expected an integer between 0 and 255

# --

# Struct's extra capabilities (provided by default):

rgb_color.to_h # {:red=>5, :green=>35, :blue=>255}

rgb_color[:red]  # 5
rgb_color['red'] # 5

{
  rgbs_colors: [
    RGBColor.new(1, 1, 255),
    RGBColor.new(5, 35, 255)
  ]
}.dig(:rgbs_colors, 1, :green) # 35