gistfile1.rb

class X
  attr_accessor :a
end

x = X.new

f = Thread.new do
  sleep 2
  x.a = "boom"
end

def wait_ready(obj, property, timeout)
  (0..timeout).each do |i|
    print '.'
    break if obj.send(property)
    sleep 1
  end
  puts
end

puts "variable a is #{x.a}"
wait_ready(x, :a, 10)
puts "variable a is #{x.a}"