Refactor internal UserDefaults observation class (#181)

Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>

Author: hank121314

Sources/Defaults/Defaults+iCloud.swift

@@ -249,11 +249,11 @@ final class iCloudSynchronizer {
 	@Atomic(value: []) private var remoteSyncingKeys: Set<Defaults.Keys>
 
 	// TODO: Replace it with async stream when Swift supports custom executors.
-	private lazy var localKeysMonitor: Defaults.CompositeUserDefaultsAnyKeyObservation = .init { [weak self] observable in
+	private lazy var localKeysMonitor: Defaults.CompositeDefaultsObservation = .init { [weak self] pair, _ in
 		guard
 			let self,
-			let suite = observable.suite,
-			let key = keys.first(where: { $0.name == observable.key && $0.suite == suite }),
+			let suite = pair.suite,
+			let key = keys.first(where: { $0.name == pair.key && $0.suite == suite }),
 			// Prevent triggering local observation when syncing from remote.
 			!remoteSyncingKeys.contains(key)
 		else {
@@ -273,7 +273,7 @@ final class iCloudSynchronizer {
 		self.keys.formUnion(keys)
 		syncWithoutWaiting(keys)
 		for key in keys {
-			localKeysMonitor.addObserver(key)
+			localKeysMonitor.add(key: key)
 		}
 	}
 
@@ -283,7 +283,7 @@ final class iCloudSynchronizer {
 	func remove(_ keys: [Defaults.Keys]) {
 		self.keys.subtract(keys)
 		for key in keys {
-			localKeysMonitor.removeObserver(key)
+			localKeysMonitor.remove(key: key)
 		}
 	}
 

Sources/Defaults/Defaults.swift

@@ -239,7 +239,7 @@ extension Defaults {
 		initial: Bool = true
 	) -> AsyncStream<Value> { // TODO: Make this `some AsyncSequence<Value>` when Swift 6 is out.
 		.init { continuation in
-			let observation = UserDefaultsKeyObservation2(object: key.suite, key: key.name) { change in
+			let observation = DefaultsObservation(object: key.suite, key: key.name) { _, change in
 				// TODO: Use the `.deserialize` method directly.
 				let value = KeyChange(change: change, defaultValue: key.defaultValue).newValue
 				continuation.yield(value)
@@ -275,7 +275,7 @@ extension Defaults {
 	) -> AsyncStream<Void> { // TODO: Make this `some AsyncSequence<Value>` when Swift 6 is out.
 		.init { continuation in
 			let observations = keys.indexed().map { index, key in
-				let observation = UserDefaultsKeyObservation2(object: key.suite, key: key.name) { _ in
+				let observation = DefaultsObservation(object: key.suite, key: key.name) { _, _ in
 					continuation.yield()
 				}
 

Sources/Defaults/Observation+Combine.swift

@@ -7,16 +7,16 @@ extension Defaults {
 	*/
 	final class DefaultsSubscription<SubscriberType: Subscriber>: Subscription where SubscriberType.Input == BaseChange {
 		private var subscriber: SubscriberType?
-		private var observation: UserDefaultsKeyObservation?
+		private var observation: DefaultsObservationWithLifeTime?
 		private let options: ObservationOptions
 
 		init(subscriber: SubscriberType, suite: UserDefaults, key: String, options: ObservationOptions) {
 			self.subscriber = subscriber
 			self.options = options
-			self.observation = UserDefaultsKeyObservation(
+			self.observation = DefaultsObservationWithLifeTime(
 				object: suite,
 				key: key,
-				callback: observationCallback(_:)
+				observationCallback
 			)
 		}
 
@@ -33,7 +33,7 @@ extension Defaults {
 			observation?.start(options: options)
 		}
 
-		private func observationCallback(_ change: BaseChange) {
+		private func observationCallback(_: SuiteKeyPair, change: BaseChange) {
 			_ = subscriber?.receive(change)
 		}
 	}