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Observable utilities for BlackbirdModel
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| // | ||
| // /\ | ||
| // | | Blackbird | ||
| // | | | ||
| // .| |. https://github.com/marcoarment/Blackbird | ||
| // $ $ | ||
| // /$ $\ Copyright 2022–2023 Marco Arment | ||
| // / $| |$ \ Released under the MIT License | ||
| // .__$| |$__. | ||
| // \/ | ||
| // | ||
| // BlackbirdObservation.swift | ||
| // Created by Marco Arment on 12/3/23. | ||
| // | ||
| // Permission is hereby granted, free of charge, to any person obtaining a copy | ||
| // of this software and associated documentation files (the "Software"), to deal | ||
| // in the Software without restriction, including without limitation the rights | ||
| // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | ||
| // copies of the Software, and to permit persons to whom the Software is | ||
| // furnished to do so, subject to the following conditions: | ||
| // | ||
| // The above copyright notice and this permission notice shall be included in all | ||
| // copies or substantial portions of the Software. | ||
| // | ||
| // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | ||
| // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | ||
| // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | ||
| // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | ||
| // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | ||
| // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE | ||
| // SOFTWARE. | ||
| // | ||
|
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| import Observation | ||
| import Combine | ||
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| // MARK: - BlackbirdModelQueryObserver | ||
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| @available(macOS 14, iOS 17, tvOS 17, watchOS 10, *) | ||
| extension BlackbirdModel { | ||
| public typealias QueryObserver<R> = BlackbirdModelQueryObserver<Self, R> | ||
| } | ||
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| @available(macOS 14, iOS 17, tvOS 17, watchOS 10, *) | ||
| @Observable | ||
| public final class BlackbirdModelQueryObserver<T: BlackbirdModel, R: Any> { | ||
| /// Whether this instance is currently loading from the database, either initially or after an update. | ||
| public var isLoading = false | ||
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| /// Whether this instance has ever loaded from the database. After the initial load, it is set to `true` and remains true. | ||
| public var didLoad = false | ||
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| /// The current instance matching the supplied primary-key value. | ||
| public var result: R? | ||
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| @ObservationIgnored private weak var database: Blackbird.Database? | ||
| @ObservationIgnored private var observer: AnyCancellable? = nil | ||
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| @ObservationIgnored private var fetcher: ((_ database: Blackbird.Database) async throws -> R) | ||
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| public init(in database: Blackbird.Database? = nil, _ fetcher: @escaping ((_ database: Blackbird.Database) async throws -> R)) { | ||
| self.fetcher = fetcher | ||
| bind(to: database) | ||
| } | ||
|
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| /// Set or change the ``Blackbird/Database`` to read from and monitor for changes. | ||
| public func bind(to database: Blackbird.Database?) { | ||
| guard let database else { return } | ||
| if let oldValue = self.database, oldValue.id == database.id { return } | ||
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| self.database = database | ||
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| observer?.cancel() | ||
| observer = nil | ||
| result = nil | ||
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| observer = T.changePublisher(in: database).sink { _ in | ||
| Task.detached { [weak self] in await self?.update() } | ||
| } | ||
| Task.detached { [weak self] in await self?.update() } | ||
| } | ||
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| let updateSemaphore = Blackbird.Semaphore(value: 1) | ||
| private func update() async { | ||
| await updateSemaphore.wait() | ||
| defer { updateSemaphore.signal() } | ||
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| await MainActor.run { | ||
| self.isLoading = true | ||
| } | ||
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| let result: R? = if let database { try? await fetcher(database) } else { nil } | ||
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| await MainActor.run { | ||
| self.result = result | ||
| self.isLoading = false | ||
| if !self.didLoad { self.didLoad = true } | ||
| } | ||
| } | ||
| } | ||
|
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| // MARK: - BlackbirdModelObserver | ||
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| @available(macOS 14, iOS 17, tvOS 17, watchOS 10, *) | ||
| extension BlackbirdModel { | ||
| public typealias Observer = BlackbirdModelObserver<Self> | ||
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| public var observer: Observer { Observer(multicolumnPrimaryKey: try! primaryKeyValues()) } | ||
| } | ||
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| @available(macOS 14, iOS 17, tvOS 17, watchOS 10, *) | ||
| @Observable | ||
| public final class BlackbirdModelObserver<T: BlackbirdModel> { | ||
| /// Whether this instance is currently loading from the database, either initially or after an update. | ||
| public var isLoading = false | ||
|
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| /// Whether this instance has ever loaded from the database. After the initial load, it is set to `true` and remains true. | ||
| public var didLoad = false | ||
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| /// The current instance matching the supplied primary-key value. | ||
| public var instance: T? | ||
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| @ObservationIgnored private weak var database: Blackbird.Database? | ||
| @ObservationIgnored private var multicolumnPrimaryKey: [Blackbird.Value]? | ||
| @ObservationIgnored private var observer: AnyCancellable? = nil | ||
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| /// Initializer to track a single-column primary-key value. | ||
| public convenience init(in database: Blackbird.Database? = nil, primaryKey: Sendable? = nil) { | ||
| self.init(in: database, multicolumnPrimaryKey: [primaryKey]) | ||
| } | ||
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| /// Initializer to track a multi-column primary-key value. | ||
| public init(in database: Blackbird.Database? = nil, multicolumnPrimaryKey: [Sendable]? = nil) { | ||
| self.multicolumnPrimaryKey = multicolumnPrimaryKey?.map { try! Blackbird.Value.fromAny($0) } ?? nil | ||
| bind(to: database) | ||
| } | ||
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| /// Set or change the ``Blackbird/Database`` to read from and monitor for changes. | ||
| public func bind(to database: Blackbird.Database?) { | ||
| guard let database else { return } | ||
| if let oldValue = self.database, oldValue.id == database.id { return } | ||
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| self.database = database | ||
| updateDatabaseObserver() | ||
| } | ||
|
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| /// Set or change the single-column primary-key value to observe. | ||
| public func observe(primaryKey: Sendable? = nil) { observe(multicolumnPrimaryKey: [primaryKey]) } | ||
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| /// Set or change the multi-column primary-key value to observe. | ||
| public func observe(multicolumnPrimaryKey: [Sendable]? = nil) { | ||
| let multicolumnPrimaryKey = multicolumnPrimaryKey?.map { try! Blackbird.Value.fromAny($0) } ?? nil | ||
| if multicolumnPrimaryKey == self.multicolumnPrimaryKey { return } | ||
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| self.multicolumnPrimaryKey = multicolumnPrimaryKey | ||
| updateDatabaseObserver() | ||
| } | ||
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| private func updateDatabaseObserver() { | ||
| observer?.cancel() | ||
| observer = nil | ||
| instance = nil | ||
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| guard let database, let multicolumnPrimaryKey else { return } | ||
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| observer = T.changePublisher(in: database, multicolumnPrimaryKey: multicolumnPrimaryKey).sink { _ in | ||
| Task.detached { [weak self] in await self?.update() } | ||
| } | ||
| Task.detached { [weak self] in await self?.update() } | ||
| } | ||
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| let updateSemaphore = Blackbird.Semaphore(value: 1) | ||
| private func update() async { | ||
| await updateSemaphore.wait() | ||
| defer { updateSemaphore.signal() } | ||
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| await MainActor.run { | ||
| self.isLoading = true | ||
| } | ||
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| let newInstance: T? = if let database, let multicolumnPrimaryKey { try? await T.read(from: database, multicolumnPrimaryKey: multicolumnPrimaryKey) } else { nil } | ||
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| await MainActor.run { | ||
| self.instance = newInstance | ||
| self.isLoading = false | ||
| if !self.didLoad { self.didLoad = true } | ||
| } | ||
| } | ||
| } | ||
|
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