iterator.cr

# The iterator pattern is a design pattern that provides a means for
# the elements of an aggregate object to be accessed sequentially without
# knowledge of its structure. This allows traversing of lists, trees and
# other structures in a standard manner.

class Fighter
  getter name, weight

  def initialize(@name : String, @weight : Int32)
  end
end

class Tournament
  include Enumerable(Fighter)

  def initialize
    @fighters = [] of Fighter
  end

  def <<(fighter)
    @fighters << fighter
  end

  def each
    @fighters.each { |fighter| yield fighter }
  end
end

# Sample
tournament = Tournament.new.tap do |t|
  t << Fighter.new "Jax", 150
  t << Fighter.new "Liu Kang", 84
  t << Fighter.new "Scorpion", 95
  t << Fighter.new "Sub-Zero", 95
  t << Fighter.new "Smoke", 252
end

p tournament.select { |fighter| fighter.weight > 100 }
            .map { |fighter| fighter.name }
# ["Jax", "Smoke"]