UITableViewCell/UICollectionViewCell input example

[ipaboy]

Hi Guys, I'm very exited with this architecture and want to thank you. While working with it I've got some questions. Could you please provide an example for the following case: I have a cell with a textfield placed on it. How should I create an Input for controller's ViewModel in this case to make it work properly with cells reusability?

Thanks.

[nmdias]

Hi @bryzinski,

Have a look at the AllPosts scene in this repository. It does what you're describing. Ping me if you need help in understanding anything in particular.

Cheers

[ipaboy]

Hi @nmdias thank you for your feedback. But unfortunately PostTableViewCell doesn't contain any UITextFields. To clarify I'm interested in a table view based form screen and looking for an elegant solution to pass rx streams of textfields (which are placed on cells) through view models's -transform method.

Probably the easiest way is to add Variable's to view model (like username, password) and bind them directly after cells are dequeued. But I love this transform function and still looking for the solution :)

[nmdias]

Hey @bryzinski,

Ah! A UITextfield! Yeah, that's different. I use a Base class. Consider the following:

class BaseTableViewCell<ViewModelType>: UITableViewCell, Reusable {
    
    private var disposeBag: DisposeBag?
    
    var viewModel: ViewModelType? {
        didSet {
            guard let viewModel = viewModel else {
                return
            }
            let disposeBag = DisposeBag()
            self.configure(viewModel, disposedBy: disposeBag)
            self.disposeBag = disposeBag
        }
    }
    
    override init(style: UITableViewCellStyle, reuseIdentifier: String?) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)
        configureDefaults()
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    public override func prepareForReuse() {
        super.prepareForReuse()
        self.disposeBag = nil
        self.viewModel = nil
    }
    
    func configureDefaults() {
        fatalError("Always override \(#function) to provide default view configurations.")
    }
    
    func configure(_ viewModel: ViewModelType, disposedBy disposeBag: DisposeBag) {
        fatalError("Always override \(#function) to provide view model configurations.")
    }
    
}

Now, with your own subclass, you could do this, maybe?

final class SomeTableViewCell: BaseTableViewCell<SomeTableViewCellViewModel> {
    
    let textfield: UITextField = {
        let textfield = UITextField()
        textfield.translatesAutoresizingMaskIntoConstraints = false
        // Do your thing
        return textfield
    }()
    
    override func configureDefaults() {
        // Do your thing
    }
    
    override func configure(_ viewModel: SomeTableViewCellViewModel, disposedBy disposeBag: DisposeBag) {
        // I suspect there might be a cleaner way to `drive` the subject...
        textfield.rx.text.asDriver().drive(onNext: { (string) in
            viewModel.text.on(.next(string))
        }).disposed(by: disposeBag)
    }
    
}

The cell has this corresponding ViewModelType:

struct SomeTableViewCellViewModel {
    let text = PublishSubject<String?>()
}

Now, when you instantiate your Cell's View Model, you can subscribe to it's text: PublishSubject<String?>

Something like:

// The Cell's View Model
viewModel.text.subscribe(onNext: { (string) in
    print(string)
}).disposed(by: disposeBag)

Then assign the Cell's viewModel

let cell = tableView.reusableCell() as SomeTableViewCell
cell.viewModel = viewModel
return cell

Does this help? Cheers

[ipaboy]

@nmdias thank you! It looks what I expected for.