67 lines
2.2 KiB
Swift
67 lines
2.2 KiB
Swift
//
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// DefaultIfEmpty.swift
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// RxSwift
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//
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// Created by sergdort on 23/12/2016.
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// Copyright © 2016 Krunoslav Zaher. All rights reserved.
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//
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extension ObservableType {
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/**
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Emits elements from the source observable sequence, or a default element if the source observable sequence is empty.
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- seealso: [DefaultIfEmpty operator on reactivex.io](http://reactivex.io/documentation/operators/defaultifempty.html)
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- parameter default: Default element to be sent if the source does not emit any elements
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- returns: An observable sequence which emits default element end completes in case the original sequence is empty
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*/
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public func ifEmpty(default: Element) -> Observable<Element> {
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DefaultIfEmpty(source: self.asObservable(), default: `default`)
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}
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}
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final private class DefaultIfEmptySink<Observer: ObserverType>: Sink<Observer>, ObserverType {
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typealias Element = Observer.Element
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private let `default`: Element
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private var isEmpty = true
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init(default: Element, observer: Observer, cancel: Cancelable) {
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self.default = `default`
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super.init(observer: observer, cancel: cancel)
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}
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func on(_ event: Event<Element>) {
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switch event {
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case .next:
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self.isEmpty = false
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self.forwardOn(event)
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case .error:
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self.forwardOn(event)
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self.dispose()
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case .completed:
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if self.isEmpty {
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self.forwardOn(.next(self.default))
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}
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self.forwardOn(.completed)
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self.dispose()
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}
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}
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}
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final private class DefaultIfEmpty<SourceType>: Producer<SourceType> {
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private let source: Observable<SourceType>
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private let `default`: SourceType
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init(source: Observable<SourceType>, `default`: SourceType) {
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self.source = source
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self.default = `default`
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}
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override func run<Observer: ObserverType>(_ observer: Observer, cancel: Cancelable) -> (sink: Disposable, subscription: Disposable) where Observer.Element == SourceType {
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let sink = DefaultIfEmptySink(default: self.default, observer: observer, cancel: cancel)
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let subscription = self.source.subscribe(sink)
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return (sink: sink, subscription: subscription)
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}
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}
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