title: How to handle multiple network call in Alamofire
body: <p>I need to call 2 apis in a view controller to fetch some data from server, I want them to start at the same time, but next step will only be triggered if both of them are returned(doesn't matter it's a success or failure).
  I can come up with 2 solutions :
  1. Chain them together. Call api1, call api2 in api1's result handler, wait for api2's result
  2. Set 2 Bool indicator variables, create a check function, if both of these indicators are true, do next. In both Apis result handler, set corresponding indicator variable, then call check function to decide if it's good to go</p>
  
  <p>First one is not sufficient enough, and I can't say the second one is a elegant solution. Does Alamofire has something like combine signal in Reactivecocoa? Or any better solution?</p>