combine-blocks.rb

class Connection
  def self.combine(*args, &block)
    # call open multiple times somehow?
  end

  def self.open(args = {}, &block)
    puts "open #{args}"
    instance = new(args)
    block.call(instance)
    puts "close #{args}"
  end

  attr_reader :args

  def initialize(args)
    puts "init #{args}"
    @args = args
  end
end

c1_args = :c1
c2_args = :c2
c3_args = :c3

# this works...

# Connection.open(c1_args) do |c1|
#   Connection.open(c2_args) do |c2|
#     Connection.open(c3_args) do |c3|
#       puts "doing stuff with #{c1.args}"
#       puts "doing stuff with #{c2.args}"
#       puts "doing stuff with #{c3.args}"
#     end
#   end
# end

# but want this API...

Connection.combine(c1_args, c2_args, c3_args) do |c1, c2, c3|
  puts "doing stuff with #{c1.args}"
  puts "doing stuff with #{c2.args}"
  puts "doing stuff with #{c3.args}"
end

# output should be...

# open c1
# init c1
# open c2
# init c2
# open c3
# init c3
# doing stuff with c1
# doing stuff with c2
# doing stuff with c3
# close c3
# close c2
# close c1