I suppose you need to use `org.robovm.apple.dispatch.DispatchQueue` to implement the `Scheduler`: https://github.com/robovm/robovm/blob/ce34632d61e20de228a0b9e2c358ae01ff2af869/cocoatouch/src/main/java/org/robovm/apple/dispatch/DispatchQueue.java

As Android `Handler` is similar to `DispatchQueue`, Android `Scheduler` should be an good example : https://github.com/Netflix/RxJava/tree/master/rxjava-contrib/rxjava-android/src/main/java/rx/android/schedulers