PromisifiedModal.swift

// Transform the presentation of a Modal VC into a promise.
// This pattern is useful when the modal has to pass some information back to the presenter
func promisifyModal() -> Promise<String> {
  return Promise<String>(in: .main) { resolve, _, _ in
    let vc = AnimalVC(store: self.store, connected: true, resolve: resolve)
    vc.modalPresentationStyle = .overFullScreen
    self.present(vc, animated: true, completion: nil)
  }
}

// Function that presents the modal and handle the data returned by it
func userTapModal() {
  self.promisifyModal()
    .then { [weak self] animal in
      // This code is invoked when the modal is dismissed.
      self?.localState.animal = animal
    }
}