86 lines
2.6 KiB
Swift
86 lines
2.6 KiB
Swift
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//
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// FetchedValueHolder.swift
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// Passepartout
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//
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// Created by Davide De Rosa on 4/8/22.
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// Copyright (c) 2022 Davide De Rosa. All rights reserved.
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//
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// https://github.com/passepartoutvpn
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//
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// This file is part of Passepartout.
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//
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// Passepartout is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// Passepartout is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with Passepartout. If not, see <http://www.gnu.org/licenses/>.
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//
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import Foundation
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import CoreData
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import Combine
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public class FetchedValueHolder<V>: NSObject, ValueHolder, NSFetchedResultsControllerDelegate {
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@Published public var value: V
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private let controller: NSFetchedResultsController<NSFetchRequestResult>
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private let mapping: ([NSFetchRequestResult]) -> V?
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public convenience init(
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context: NSManagedObjectContext,
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request: NSFetchRequest<NSFetchRequestResult>,
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mapping: @escaping ([NSFetchRequestResult]) -> V?,
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initial: V
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) {
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let controller = NSFetchedResultsController(
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fetchRequest: request,
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managedObjectContext: context,
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sectionNameKeyPath: nil,
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cacheName: nil
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)
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self.init(controller: controller, mapping: mapping, initial: initial)
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}
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public init(
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controller: NSFetchedResultsController<NSFetchRequestResult>,
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mapping: @escaping ([NSFetchRequestResult]) -> V?,
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initial: V
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) {
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self.controller = controller
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self.mapping = mapping
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value = initial
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super.init()
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controller.delegate = self
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do {
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try controller.performFetch()
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} catch {
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pp_log.error("Unable to perform initial fetch: \(error)")
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}
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mapResults()
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}
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public func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
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mapResults()
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}
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private func mapResults() {
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guard let results = controller.fetchedObjects else {
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return
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}
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pp_log.verbose("Results: \(results)")
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guard let newValue = mapping(results) else {
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return
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}
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value = newValue
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}
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}
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