We'll continue today with another intuitive and expressive method in Ruby: Integer#times.

5.times do |i|
  puts i
end

# Output:
# 0
# 1
# 2
# 3
# 4
      

for (let i = 0; i < 5; i++) {
  console.log(i);
}

// Output:
// 0
// 1
// 2
// 3
// 4
      

Since times returns an Enumerator, we can leverage that by chaining map to create an array of a certain size with values derived from the index:

squares = 10.times.map { |i| i * i }
# => [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
      

const squares = Array.from({ length: 10 }, (_, i) => i * i);
// => [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
      

A personal favorite use case is spawning multiple threads to perform concurrent work:

NUMBER_OF_WORKERS = 5

threads = NUMBER_OF_WORKERS.times.map do
  Thread.new do
    # perform some work
  end
end

results = threads.each(&:value)
    

Or how about generating some test data:

ten_users = 10.times.map do |i|
  {
    name: "User #{i}",
    email: "user#{i}@example.com"
  }
end

User.insert_all(ten_users)
    

Beautiful, isn't it?

History

The times method has been around in Ruby since at least version 1.8, though it was originally a method on Fixnum and Bignum, which were unified into Integer in Ruby 2.4.

As is becoming a pattern, we can trace the idea of a "times" API back to Smalltalk's timesRepeat as well as Lisp's dotimes. No recent languages appear to have a similar construct built-in, settling for conventional "computer language" like for ... instead.