SoompiBlog - ActionController FollowAction.pseudo.swift

  func perform(followAction: FollowAction,
               cache: Cache<FanClub>,
               updateHandler: @escaping (_ isRevertOnFailure: Bool) -> Void) {
    // update cache optimistically
    let originalFanClub = cache.value(for: followAction.fanClubId)
    if let updatedFanClub = originalFanClub?.updated(with: followAction) {
      cache.set(updatedFanClub, for: followAction.fanClubId)
    }
    updateHandler(false)
    lastFollowActionUpdatedAt = Date()

    // send network request
    apiClient.followFanClub(id: followAction.fanClubId, isOn: followAction.isOn)
      .observeOn(MainScheduler.instance)
      .subscribe(onCompleted: nil, onError: { [weak self] error in
        guard let weakSelf = self else { return }
        weakSelf.delegate?.actionController(weakSelf, didReceive: error)

        // revert on failure
        if let originalFanClub = originalFanClub {
          cache.set(originalFanClub, for: followAction.fanClubId)
        }
        updateHandler(true)
      })
      .disposed(by: disposeBag)
  }