mulit-conns.rb

##
#
class Connection
  def self.create_many(inits)
    inits.map { |init| new(init) }
  end

  def self.for_all(conns, &block)
    block.call(conns)
  end

  def self.open_all(conns)
    conns.each(&:open)
  end

  def self.close_all(conns)
    conns.each(&:close)
  end

  attr_reader :args

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

  def open
    puts "open #{@args}"
  end

  def close
    puts "close #{@args}"
  end
end

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

inits = [c1_args, c2_args, c3_args]
conns = Connection.create_many(inits)
Connection.open_all(conns)

Connection.for_all(conns) do |c1, c2, c3|
  puts "doing stuff with #{c1.args}"
  puts "doing stuff with #{c2.args}"
  puts "doing stuff with #{c3.args}"
end

Connection.close_all(conns)

# output is ...
#
# init c1
# init c2
# init c3
# open c1
# open c2
# open c3
# doing stuff with c1
# doing stuff with c2
# doing stuff with c3
# close c1
# close c2
# close c3

# 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