How does ReactiveCocoa bind the ImageView, listen to the ImageView and perform the setImage method?

[CavanLife]

How does ReactiveCocoa bind the ImageView, listen to the ImageView and perform the setImage method?

[andersio]

UIImageView can be bound with any ReactiveSwift primitive via its image binding target, as long as the RHS would not fail.

For example:

// `fetchAvatarFromNetwork` returns `SignalProducer<UIImage, MyError>`.

imageView.reactive.image <~ fetchAvatarFromNetwork()
    // Ignore the error if the request has failed. So the placeholder would stay.
    .flatMapError { _ in .empty }
    // Set the image immediately to the placeholder.
    .prefix(value: avatarPlaceholder)