RxSwift/RxRelay/BehaviorRelay.swift

//
//  BehaviorRelay.swift
//  RxRelay
//
//  Created by Krunoslav Zaher on 10/7/17.
//  Copyright © 2017 Krunoslav Zaher. All rights reserved.
//

import RxSwift

/// BehaviorRelay is a wrapper for `BehaviorSubject`.
///
/// Unlike `BehaviorSubject` it can't terminate with error or completed.
public final class BehaviorRelay<Element>: ObservableType {
    public typealias E = Element

    private let _subject: BehaviorSubject<Element>

    /// Accepts `event` and emits it to subscribers
    public func accept(_ event: Element) {
        self._subject.onNext(event)
    }

    /// Current value of behavior subject
    public var value: Element {
        // this try! is ok because subject can't error out or be disposed
        return try! self._subject.value()
    }

    /// Initializes behavior relay with initial value.
    public init(value: Element) {
        self._subject = BehaviorSubject(value: value)
    }

    /// Subscribes observer
    public func subscribe<O: ObserverType>(_ observer: O) -> Disposable where O.E == E {
        return self._subject.subscribe(observer)
    }

    /// - returns: Canonical interface for push style sequence
    public func asObservable() -> Observable<Element> {
        return self._subject.asObservable()
    }
}