Creating own observer for bind(to:)

📚 Official Books RxSwift
1

Hi, in my custom cell I have something like this:

var title: String? {
    get {
        return titleLabel.text
    }
    set {
        titleLabel.text = newValue?.uppercased()
        titleLabel.addTextSpacing()
        // maybe something more
    }
}

and in order to use (in a reactive way) in my VC I have to use this long code

        viewModel
            .titleObs // Observable<String?>
            .subscribe(onNext: { title in
                cell.title = title
            })
            .addDisposableTo(cell.bag)

I’m not sure if it was in the book, maybe I missed it out, but is it possible to create a custom receiver for bind(to:) method? I know I can bind titleObs directly to titleLabel.rx.text, but I need to add some more work. even more, than I gave here in the example.
I would like to make something like this:

// VC
viewModel
    .titleObs // Observable<String?>
    .bind(to: cell.title)
    .addDisposableTo(cell.bag)

// Cell    
var title: Binder<String?> {
    titleLabel.text = newValue?.uppercased()
    titleLabel.addTextSpacing()
    // maybe something more
}
2

Ok i found solution, but I don’t know why I can’t delete the topic.

1 Like
3

Don’t worry about deleting the topic, let it stay so other who have similar questions can find it :slight_smile:

4

OK :blush:
@icanzilb can you explain why did you use .asObserver() and not leave UIBindingObserver just as is in your example? What’s the difference?

5

asObserver() returns an AnyObserver instance type erasing the actual observer implementation. So when you have a custom observer class of your own, let’s say MarinObserver you can’t use it with bind(to:) which expects AnyObserver (e.g. AnyObserver implements the minimal observer interface). That’s why when you return toObserver() you return type-erased observer which you can use for binding, but under the hood it’s still your custom observer that does the work.