//
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// ElementAt.swift
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// RxSwift
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//
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// Created by Junior B. on 21/10/15.
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// Copyright © 2015 Krunoslav Zaher. All rights reserved.
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//
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extension ObservableType {
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/**
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Returns a sequence emitting only element _n_ emitted by an Observable
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- seealso: [elementAt operator on reactivex.io](http://reactivex.io/documentation/operators/elementat.html)
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- parameter index: The index of the required element (starting from 0).
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- returns: An observable sequence that emits the desired element as its own sole emission.
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*/
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@available(*, deprecated, renamed: "element(at:)")
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public func elementAt(_ index: Int)
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-> Observable<Element> {
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element(at: index)
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}
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/**
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Returns a sequence emitting only element _n_ emitted by an Observable
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- seealso: [elementAt operator on reactivex.io](http://reactivex.io/documentation/operators/elementat.html)
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- parameter index: The index of the required element (starting from 0).
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- returns: An observable sequence that emits the desired element as its own sole emission.
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*/
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public func element(at index: Int)
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-> Observable<Element> {
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ElementAt(source: self.asObservable(), index: index, throwOnEmpty: true)
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}
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}
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final private class ElementAtSink<Observer: ObserverType>: Sink<Observer>, ObserverType {
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typealias SourceType = Observer.Element
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typealias Parent = ElementAt<SourceType>
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let parent: Parent
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var i: Int
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init(parent: Parent, observer: Observer, cancel: Cancelable) {
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self.parent = parent
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self.i = parent.index
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super.init(observer: observer, cancel: cancel)
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}
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func on(_ event: Event<SourceType>) {
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switch event {
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case .next:
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if self.i == 0 {
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self.forwardOn(event)
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self.forwardOn(.completed)
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self.dispose()
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}
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do {
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_ = try decrementChecked(&self.i)
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} catch let e {
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self.forwardOn(.error(e))
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self.dispose()
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return
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}
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case .error(let e):
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self.forwardOn(.error(e))
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self.dispose()
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case .completed:
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if self.parent.throwOnEmpty {
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self.forwardOn(.error(RxError.argumentOutOfRange))
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} else {
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self.forwardOn(.completed)
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}
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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 ElementAt<SourceType>: Producer<SourceType> {
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let source: Observable<SourceType>
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let throwOnEmpty: Bool
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let index: Int
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init(source: Observable<SourceType>, index: Int, throwOnEmpty: Bool) {
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if index < 0 {
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rxFatalError("index can't be negative")
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}
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self.source = source
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self.index = index
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self.throwOnEmpty = throwOnEmpty
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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 = ElementAtSink(parent: self, 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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