Let Me Check My Scheduler

FollowUserViewModel.pt1.swift

final class FollowUserViewModel {
  // Observer for our view to bind to when our user
  // wants to follow another user.
  let followUserObserver: AnyObserver<User> {
    return followSubject.asObserver()
  }
  private let disposeBag = DisposeBag()
  // This subject will listen for users to follow.
  private let followSubject = PublishSubject<User>()
  init(user: User, networkHandler: FollowNetworkHandler) {
    // Create an operation queue to do work on
    let operationQueue = OperationQueue()
    operationQueue.maxConcurrentOperationCount = 20
    // Set it to the .userInitiated Quality Of Service
    operationQueue.qualityOfService = .userInitiated
    // Create a scheduler with our new OperationQueue
    // A Scheduler defines what queue our work will happen on.
    // By specifying our background scheduler, we ensure work will
    // not block interaction with the user.
    let backgroundScheduler = OperationQueueScheduler(
      operationQueue: operationQueue
    )
    followSubject
    // Perform our work onto the our scheduler
    .observeOn(backgroundScheduler)
    .do(onNext: { [weak self] user in
    // Perform the follow when an event comes in.
      networkHandler.follow(user: user)
    })
    .subscribe()
    .disposed(by: disposeBag)
  }
}