Protocol.swift

import JavaScriptKit

@JS protocol MyViewControllerDelegate {
    func onSomethingHappened()
    func onValueChanged(_ value: String)
    func onCountUpdated(count: Int) -> Bool
    func onLabelUpdated(_ prefix: String, _ suffix: String)
    func isCountEven() -> Bool
}

@JS class MyViewController {
    @JS
    var delegate: MyViewControllerDelegate

    @JS
    var secondDelegate: MyViewControllerDelegate?

    @JS init(delegate: MyViewControllerDelegate) {
        self.delegate = delegate
    }

    @JS func triggerEvent() {
        delegate.onSomethingHappened()
    }

    @JS func updateValue(_ value: String) {
        delegate.onValueChanged(value)
    }

    @JS func updateCount(_ count: Int) -> Bool {
        return delegate.onCountUpdated(count: count)
    }

    @JS func updateLabel(_ prefix: String, _ suffix: String) {
        delegate.onLabelUpdated(prefix, suffix)
    }

    @JS func checkEvenCount() -> Bool {
        return delegate.isCountEven()
    }
}