I've passed this question. Still I have an issue
Why do I need to check whether prime_array is assigned yet or not? (line 14)
The prime_array is existed only in the function first_n_primes, right? This means after first_n_primes finished its task, prime_array will be deleted. So the next time using first_n_primes, prime_array will be brand new. Then why do I need to add ||= ?
$VERBOSE = nil # We'll explain this at the end of the lesson. require 'prime' # This is a module. We'll cover these soon! def first_n_primes(n) unless n.is_a? Integer return "n must be an integer." end if n <= 0 return "n must be greater than 0." end prime_array ||=  #line 14 prime = Prime.new for num in (1..n) prime_array.push(prime.next) end return prime_array end first_n_primes(10)