//
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// CompactMap.swift
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// RxSwift
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//
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// Created by Michael Long on 04/09/2019.
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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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Projects each element of an observable sequence into an optional form and filters all optional results.
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- parameter transform: A transform function to apply to each source element and which returns an element or nil.
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- returns: An observable sequence whose elements are the result of filtering the transform function for each element of the source.
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*/
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public func compactMap<Result>(_ transform: @escaping (Element) throws -> Result?)
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-> Observable<Result> {
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CompactMap(source: self.asObservable(), transform: transform)
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}
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}
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final private class CompactMapSink<SourceType, Observer: ObserverType>: Sink<Observer>, ObserverType {
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typealias Transform = (SourceType) throws -> ResultType?
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typealias ResultType = Observer.Element
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typealias Element = SourceType
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private let transform: Transform
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init(transform: @escaping Transform, observer: Observer, cancel: Cancelable) {
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self.transform = transform
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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(let element):
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do {
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if let mappedElement = try self.transform(element) {
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self.forwardOn(.next(mappedElement))
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}
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}
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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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}
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case .error(let error):
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self.forwardOn(.error(error))
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self.dispose()
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case .completed:
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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 CompactMap<SourceType, ResultType>: Producer<ResultType> {
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typealias Transform = (SourceType) throws -> ResultType?
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private let source: Observable<SourceType>
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private let transform: Transform
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init(source: Observable<SourceType>, transform: @escaping Transform) {
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self.source = source
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self.transform = transform
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}
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override func run<Observer: ObserverType>(_ observer: Observer, cancel: Cancelable) -> (sink: Disposable, subscription: Disposable) where Observer.Element == ResultType {
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let sink = CompactMapSink(transform: self.transform, 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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