Constants on Object

class Animal

FOOD = ["grass", "meat"]

end

p Animal.constants

# Output:

$ruby main.rb

[:FOOD]

With some libraries:

[36] pry(main)> Integer.constants

=> []

[37] pry(main)> Float.constants

=> [:ROUNDS, :RADIX, :MANT_DIG, :DIG, :MIN_EXP, :MAX_EXP, :MIN_10_EXP, :MAX_10_EXP, :MIN, :MAX, :EPSILON, :INFINITY, :NAN]