yield_blocks.cr

module Blocks
  
  NUMBERS = [1,2,3]
  
  def self.require_block(&block)
    NUMBERS.each do |number|
      yield number
    end
  end

  # because method overloading
  def self.optional_block
    NUMBERS
  end

  def self.optional_block(&block)
    require_block do |number|
      yield number
    end
  end
  
end

Blocks.require_block do |number|
  puts number
end

Blocks.optional_block.each do |number|
  puts number
end

Blocks.optional_block do |number|
  puts number
end