Simple observable

Very simple Observable and Publisher implementation for iOS apps.

Useful if you want to use a bit of simple reactive programming but do not want to add the full RxSwift or use Combine.

Observable

Create an Observable instance providing a default value.

let isLoading = Observable<Bool>(false)

you can assign and read the value of this observable using the value property, for example when using it in a view model

isLoading.value = true

You can bind to the value changes using the bind function, for example in a view controller

viewModel.isLoading.bind { [weak self] isLoading in
    self?.loadingView.isHidden = !isLoading
}

You can also use a version of bind that accepts a keypath

viewModel.isLoading.bind(to: userDetailsView, keyPath: \.isHidden)

Publisher is an observable without an initial value. An Observable is used for storing state, a Publisher is used for events.

After you create a Publisher instance

let onError = Publisher<Error>()

you can publish new values to this publisher with the publish method, for example when using it in a view model

onError.publish(ApiError.InvalidCredentials)

You can bind to the value changes using the bind function, for example in a view controller

viewModel.onError.bind { [weak self] error in
    self?.showAlert(error)
}

ObservableButton can be created in code or used from a storyboard. You can use the ObservableButton to easily subscribe to the tap event

loginButton.observable.tap.bind { [weak self] in
    self?.login()
}

You can bind to an observable or an publisher just once. This is not a technical limitation but a design decision.

Boith observable and publisher always call the bind method on the main thread so no need to worry about binding changes to UI elements.