RxPagination

This is the demo project for my presentation at try! Swift conference 2016.

• Slides: https://speakerdeck.com/ishkawa/protocol-oriented-programming-in-networking
• Video: https://news.realm.io/news/tryswift-yosuke-ishikawa-protocol-oriented-networking/

Set Up

• carthage bootstrap --platform iOS

Requirements

• Swift 3.0.1
• Xcode 8.1

Summary

This demo project illustrates how to use RxSwift, Action and APIKit. The demo app fetches repositories via GitHub search API and displays them using the libraries.

<img src="screenshot.png" width=320>

ViewModel

PaginationViewModel<Element> is a view model for pagination. It has an initializer with type parameter Request, which is constrained to conform to PaginationRequest protocol. When PaginationViewModel<Element> is instantiated via init<Request>(baseRequest:), the type of its property that represents pagination elements will be inferred as Observable<[Request.Response.Element]>.

class PaginationViewModel<Element: Decodable> {
    let indicatorViewAnimating: Driver<Bool>
    let elements: Driver<[Element]>
    let loadError: Driver<Error>

    init<Request: PaginationRequest>(
        baseRequest: Request,
        viewWillAppear: Driver<Void>,
        scrollViewDidReachBottom: Driver<Void>) where Request.Response.Element == Element {...}
}

ViewController

Once ViewModel is instantiated with a Request type parameter, remained task that ViewController have to do is binding input streams and output streams.

class SearchRepositoriesViewController: UITableViewController {
    @IBOutlet weak var indicatorView: UIActivityIndicatorView!

    private let disposeBag = DisposeBag()
    private var viewModel: PaginationViewModel<Repository>!

    override func viewDidLoad() {
        super.viewDidLoad()

        let baseRequest = GitHubAPI.SearchRepositoriesRequest(query: "Swift")

        viewModel = PaginationViewModel(
            baseRequest: baseRequest,
            viewWillAppear: rx.viewWillAppear.asDriver(),
            scrollViewDidReachBottom: tableView.rx.reachedBottom.asDriver())

        disposeBag.insert([
            viewModel.indicatorViewAnimating.drive(indicatorView.rx.isAnimating),
            viewModel.elements.drive(tableView.rx.items(cellIdentifier: "Cell", cellType: RepositoryCell.self)),
            viewModel.loadError.drive(onNext: { print($0) }),
        ])
    }
}

Contact

Twitter: https://twitter.com/_ishkawa