Ruby Koans #75 test_constants_become_symbols, correct answer?
ruby, symbols
Solution
NOTE: the following answer only applies to environments like irb, where Ruby code is being executed line by line. When executing code in a file, Ruby scans the entire file for symbols before executing anything, so the following details are not accurate. I've not deleted this answer because it exposes an interesting edge case, but see @GlichMr's answer for a better explanation of the problem.
You can safely do the following, because `Symbol.all_symbols` returns a copy of the array of symbols, not a reference.
assert_equal true, all_symbols.include?(:RubyConstant)
I think that is the intended answer to the koan, and it's why `all_symbols` is defined rather than calling `Symbol.all_symbols` directly. For some evidence, see the following:
>> X = 1
=> 1
>> all_symbols = Symbol.all_symbols; nil
=> nil
>> Y = 2
=> 2
>> all_symbols.include?(:X)
=> true
>> all_symbols.include?(:Y)
=> false
Using `String#to_sym` would make it possible to make these calls against `Symbol.all_symbols` directly, but is not necessary for solving this koan.
Problem
My question builds upon this question: Ruby Koan: Constants become symbols. I have the following code: ``` in_ruby_version("mri") do RubyConstant = "What is the sound of one hand clapping?" def test_constants_become_symbols all_symbols = Symbol.all_symbols assert_equal __, all_symbols.include?(__) end end ``` Is the correct answer supposed to be the following? ``` assert_equal true, all_symbols.include?("RubyConstant".to_sym) ``` I know I shouldn't just do this: ``` assert_equal true, all_symbols.include?(:RubyConstant) ``` because then I could put anything in there and it would still be true ``` assert_equal true, all_symbols.include?(:DoesNotMatter) ``` Apologies in advance for asking simple a "yes or no" question. I was curious as to know what the "right" answer is. I would have preferred to just ask this question in the comments in the previous post I mentioned above but I couldn't without making a separate post.