124 lines
3.3 KiB
Swift
124 lines
3.3 KiB
Swift
import Foundation
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import Combine
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extension Defaults {
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/**
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Custom `Subscription` for `UserDefaults` key observation.
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*/
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final class DefaultsSubscription<SubscriberType: Subscriber>: Subscription where SubscriberType.Input == BaseChange {
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private var subscriber: SubscriberType?
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private var observation: UserDefaultsKeyObservation?
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private let options: ObservationOptions
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init(subscriber: SubscriberType, suite: UserDefaults, key: String, options: ObservationOptions) {
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self.subscriber = subscriber
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self.options = options
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self.observation = UserDefaultsKeyObservation(
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object: suite,
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key: key,
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callback: observationCallback(_:)
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)
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}
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func request(_ demand: Subscribers.Demand) {
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// Nothing as we send events only when they occur.
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}
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func cancel() {
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observation = nil
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subscriber = nil
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}
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func start() {
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observation?.start(options: options)
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}
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private func observationCallback(_ change: BaseChange) {
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_ = subscriber?.receive(change)
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}
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}
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/**
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Custom Publisher, which is using DefaultsSubscription.
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*/
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struct DefaultsPublisher: Publisher {
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typealias Output = BaseChange
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typealias Failure = Never
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private let suite: UserDefaults
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private let key: String
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private let options: ObservationOptions
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init(suite: UserDefaults, key: String, options: ObservationOptions) {
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self.suite = suite
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self.key = key
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self.options = options
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}
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func receive(subscriber: some Subscriber<Output, Failure>) {
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let subscription = DefaultsSubscription(
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subscriber: subscriber,
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suite: suite,
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key: key,
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options: options
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)
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subscriber.receive(subscription: subscription)
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subscription.start()
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}
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}
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/**
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Returns a type-erased `Publisher` that publishes changes related to the given key.
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```swift
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extension Defaults.Keys {
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static let isUnicornMode = Key<Bool>("isUnicornMode", default: false)
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}
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let publisher = Defaults.publisher(.isUnicornMode).map(\.newValue)
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let cancellable = publisher.sink { value in
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print(value)
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//=> false
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}
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```
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- Warning: This method exists for backwards compatibility and will be deprecated sometime in the future. Use ``Defaults/updates(_:initial:)-9eh8`` instead.
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*/
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public static func publisher<Value: Serializable>(
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_ key: Key<Value>,
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options: ObservationOptions = [.initial]
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) -> AnyPublisher<KeyChange<Value>, Never> {
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let publisher = DefaultsPublisher(suite: key.suite, key: key.name, options: options)
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.map { KeyChange<Value>(change: $0, defaultValue: key.defaultValue) }
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return AnyPublisher(publisher)
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}
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/**
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Publisher for multiple `Key<T>` observation, but without specific information about changes.
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- Warning: This method exists for backwards compatibility and will be deprecated sometime in the future. Use ``Defaults/updates(_:initial:)-9eh8`` instead.
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*/
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public static func publisher(
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keys: _AnyKey...,
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options: ObservationOptions = [.initial]
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) -> AnyPublisher<Void, Never> {
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let initial = Empty<Void, Never>(completeImmediately: false).eraseToAnyPublisher()
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let combinedPublisher =
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keys
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.map { key in
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DefaultsPublisher(suite: key.suite, key: key.name, options: options)
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.map { _ in () }
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.eraseToAnyPublisher()
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}
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.reduce(initial) { combined, keyPublisher in
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combined.merge(with: keyPublisher).eraseToAnyPublisher()
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}
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return combinedPublisher
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}
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}
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