[iOS] RxSwift/RxCocoa/RxRelay - Subject와 Relay

UI이기 때문에 PublishSubject 대신 PublishRelay를 쓰는 코드를 봤다. 차이가 뭔데? 궁금해서 정의 찾아봄

 

Pods > RxRelay > PublishRelay

아 참고로 RxSwift Github 공식 README.md에 가보면 RxSwift, RxCocoa, RcRelay 등의 연관 관계를 설명해주고 있다. 

https://github.com/ReactiveX/RxSwift

//
//  PublishRelay.swift
//  RxRelay
//
//  Created by Krunoslav Zaher on 3/28/15.
//  Copyright © 2017 Krunoslav Zaher. All rights reserved.
//

import RxSwift

/// PublishRelay is a wrapper for `PublishSubject`.
///
/// Unlike `PublishSubject` it can't terminate with error or completed.
public final class PublishRelay<Element>: ObservableType {
    private let subject: PublishSubject<Element>
    
    // Accepts `event` and emits it to subscribers
    public func accept(_ event: Element) {
        self.subject.onNext(event)
    }
    
    /// Initializes with internal empty subject.
    public init() {
        self.subject = PublishSubject()
    }

    /// Subscribes observer
    public func subscribe<Observer: ObserverType>(_ observer: Observer) -> Disposable where Observer.Element == Element {
        self.subject.subscribe(observer)
    }
    
    /// - returns: Canonical interface for push style sequence
    public func asObservable() -> Observable<Element> {
        self.subject.asObservable()
    }
}

주석에 잘 써져 있다.

PublishRelay is a wrapper for `PublishSubject`.

PublishRelay는 PublishSubject의 wrapper Class이며, 

Unlike `PublishSubject` it can't terminate with error or completed.

PublishSubject와 달리 error나 completed를 받아도 종료되지 않는다.