LazyBehaviorRelay.swift

final class LazyBehaviorRelay<Element>: ObservableType, ObserverType {
    private let _behaviorRelay = BehaviorRelay<Element?>(value: nil)
    private let _emittedValue: Observable<Element>
    
    init() {
        _emittedValue = _behaviorRelay
            .filterNil()
            .share(replay: 1, scope: .forever)
    }
    
    /// Current value of behavior subject
    public var value: Element? {
        return _behaviorRelay.value
    }
    
    func accept(_ event: Element) {
        _behaviorRelay.accept(event)
    }
    
    // MARK: - ObservableType
    
    func subscribe<Observer>(_ observer: Observer) -> Disposable where Observer: ObserverType, Element == Observer.Element {
        _emittedValue.subscribe(observer)
    }
    
    // MARK: - ObserverType
    
    func on(_ event: RxSwift.Event<Element>) {
        switch event {
        case let .next(value):
            _behaviorRelay.accept(value)
        case .error, .completed:
            break
        }
    }
}