Correct usage of RxSwift with TableView - mvvm

Question

I don't know how transfer the data between ModelView and ViewController. In
SelectModelViewController
class SelectModelViewController: UIViewController {
#IBOutlet weak var tableView: UITableView!
#IBOutlet weak var errorLabel: UILabel!
#IBOutlet weak var activityIndicator: UIActivityIndicatorView!
var markViewModel : MarkViewModel?
let markService = MarkService()
let disposeBag = DisposeBag()
override func viewDidLoad() {
super.viewDidLoad()
markViewModel = MarkViewModel(markService: markService)
markViewModel?.data.asObservable()
.bindTo(tableView.rx.items(cellIdentifier: "Cell", cellType: UITableViewCell.self)) { (_, element, cell) in
cell.textLabel?.text = element
}
.addDisposableTo(disposeBag)
}
}
MarkViewModel has an error. I'am doing something wrong
struct MarkViewModel {
let markService: MarkService
var data: Driver<[Mark]>
init(markService: MarkService) {
self.markService = markService
data = markService.get()
.map { result in
switch result {
case.success(let marks):
return marks.map { mark in
return mark
}
case .error(let error):
print(error)
}
}.asDriver(onErrorJustReturn: .error(.other))
}}
MarkService
struct MarkService {
func get() -> Observable<Result<[Mark]>> {
return URLSession.shared.rx.json(url: URL(string: API.BaseURL)!)
.retry(3)
.map {
var marks = [Mark]()
guard let json = $0 as? [String: Any],
let items = json["RBMarks"] as? [[String : Any]] else {
return .error(.badJSON)
}
for item in items {
if let mark = Mark(json: item) {
marks.append(mark)
} else {
return .error(.badJSON)
}
}
return .success(marks)
}
.catchErrorJustReturn(.error(.noInternet))
}}

Answer 1

First, we can return Observable<Result<[Mark]>> from MarkService instead of Any. This will be useful later on to display them.
struct MarkService {
func get() -> Observable<Result<[Mark]>> {
return URLSession.shared.rx.json(url: URL(string: API.BaseURL)!)
.retry(3)
.map {
var marks = [Mark]()
guard let json = $0 as? [String: Any],
let items = json["RBMarks"] as? [[String : Any]] else {
return .error(.badJSON)
}
for item in items {
if let mark = Mark(json: item) {
marks.append(mark)
} else {
return .error(.badJSON)
}
}
return .success(marks)
}
.catchErrorJustReturn(.error(.noInternet))
}
}
Then, let's remove the subscription to data in MarkViewModel. We'll also transform the marks to something that is more suited for presentation.
struct MarkViewModel {
let markService: MarkService
var data: Driver<[String]>
var marks: Variable<[Mark]>
let disposeBag = DisposeBag()
init(markService: MarkService) {
self.markService = markService
data = markService.get()
.map { result in
guard case .success(let marks) = result else {
return ["Error while getting marks"]
}
return marks.map { mark in
"For assignment \(mark.assignmentName), you were marked with \(mark.grade)/10"
}
}
.asDriver(onErrorJustReturn: .error(.other))
}
}
Now, in view controller, we can use RxSwift's table view bindings to display those data
let disposeBag = DisposeBag()
func viewDidLoad() {
viewModel.data
.bindTo(tableView.rx.items(cellIdentifier: "Cell", cellType: UITableViewCell.self)) { (_, element, cell) in
cell.textLabel?.text = element
}
.addDisposableTo(disposeBag)
}
This is obviously only an example of how you could do it and code will change depending on the requirements for specific views.