RxSwift ViewModel Example

Example of a ViewModel with RxSwift

1. Protocol:

    protocol TaskListViewModelType {

        // Input

        var addButtonDidTap: PublishSubject<Void> { get }

        var itemDidSelect: PublishSubject<NSIndexPath> { get }

        var itemDeleted: PublishSubject<NSIndexPath> { get }


        // Output

        var navigationBarTitle: Driver<String?> { get }

        var sections: Driver<[TaskListSection]> { get }

        var presentTaskEditViewModel: Driver<TaskEditViewModelType> { get }
    }

1. ViewModel, conforms to protocol:

    struct TaskListViewModel: TaskListViewModelType {
   
        // MARK: Input
   
        let addButtonDidTap = PublishSubject<Void>()
   
        let itemDidSelect = PublishSubject<NSIndexPath>()
   
        var itemDeleted = PublishSubject<NSIndexPath>()
   

        // MARK: Output

        let navigationBarTitle: Driver<String?>

        let sections: Driver<[TaskListSection]>

        let presentTaskEditViewModel: Driver<TaskEditViewModelType>


        // MARK: Private

        private let disposeBag = DisposeBag()

        private var tasks: Variable<[Task]>

1. Initializer:

        init() {
   
            let defaultTasks = [
   
            Task(title: "Go to https://github.com/devxoul"),
   
            Task(title: "Star repositories I am intersted in"),
   
            Task(title: "Make a pull request"),
   
            ]
   
            let tasks = Variable<[Task]>(defaultTasks)
   
            self.tasks = tasks
   
            self.navigationBarTitle = .just("Tasks")
   
            self.sections = tasks.asObservable()
   
            .map { tasks in
   
                let cellModels = tasks.map(TaskCellModel.init) as [TaskCellModelType]
   
                let section = TaskListSection(model: Void(), items: cellModels)
   
                return [section]
            }
   
            .asDriver(onErrorJustReturn: )
   

            self.itemDeleted

                .subscribeNext { indexPath in

                    let task = tasks.value[indexPath.row]

                    Task.didDelete.onNext(task)
            }

            .addDisposableTo(self.disposeBag)

1. Continuation of Initializer - ViewController Navigation

        // View Controller Navigations
   

        let presentAddViewModel: Observable<TaskEditViewModelType> = self.addButtonDidTap

            .map { TaskEditViewModel(mode: .New) }


        let presentEditViewModel: Observable<TaskEditViewModelType> = self.itemDidSelect

            .map { indexPath in

                let task = tasks.value[indexPath.row]

                return TaskEditViewModel(mode: .Edit(task))
            }


        self.presentTaskEditViewModel = Observable.of(presentAddViewModel,
             presentEditViewModel).merge()

            .asDriver(onErrorDriveWith: .empty())

1. Continuation of Initializer - Model Service

        // Model Service

        Task.didCreate

        .subscribeNext { task in

            self.tasks.value.insert(task, atIndex: 0)

        }
        .addDisposableTo(self.disposeBag)


        Task.didUpdate

            .subscribeNext { task in

                if let index = self.tasks.value.indexOf(task) {

                    self.tasks.value[index] = task
                }
            }
            .addDisposableTo(self.disposeBag)


        Task.didDelete

            .subscribeNext { task in

                if let index = self.tasks.value.indexOf(task) {

                    self.tasks.value.removeAtIndex(index)
                }

            }
            .addDisposableTo(self.disposeBag)

        }
    }