//
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// AnyObserver.swift
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// RxSwift
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//
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// Created by Krunoslav Zaher on 2/28/15.
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// Copyright © 2015 Krunoslav Zaher. All rights reserved.
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//
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/// A type-erased `ObserverType`.
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///
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/// Forwards operations to an arbitrary underlying observer with the same `Element` type, hiding the specifics of the underlying observer type.
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public struct AnyObserver<Element> : ObserverType {
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/// Anonymous event handler type.
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public typealias EventHandler = (Event<Element>) -> Void
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private let observer: EventHandler
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/// Construct an instance whose `on(event)` calls `eventHandler(event)`
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///
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/// - parameter eventHandler: Event handler that observes sequences events.
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public init(eventHandler: @escaping EventHandler) {
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self.observer = eventHandler
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}
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/// Construct an instance whose `on(event)` calls `observer.on(event)`
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///
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/// - parameter observer: Observer that receives sequence events.
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public init<Observer: ObserverType>(_ observer: Observer) where Observer.Element == Element {
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self.observer = observer.on
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}
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/// Send `event` to this observer.
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///
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/// - parameter event: Event instance.
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public func on(_ event: Event<Element>) {
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self.observer(event)
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}
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/// Erases type of observer and returns canonical observer.
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///
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/// - returns: type erased observer.
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public func asObserver() -> AnyObserver<Element> {
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self
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}
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}
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extension AnyObserver {
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/// Collection of `AnyObserver`s
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typealias s = Bag<(Event<Element>) -> Void>
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}
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extension ObserverType {
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/// Erases type of observer and returns canonical observer.
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///
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/// - returns: type erased observer.
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public func asObserver() -> AnyObserver<Element> {
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AnyObserver(self)
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}
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/// Transforms observer of type R to type E using custom transform method.
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/// Each event sent to result observer is transformed and sent to `self`.
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///
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/// - returns: observer that transforms events.
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public func mapObserver<Result>(_ transform: @escaping (Result) throws -> Element) -> AnyObserver<Result> {
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AnyObserver { e in
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self.on(e.map(transform))
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}
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}
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}
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