91 lines
3.1 KiB
Swift
91 lines
3.1 KiB
Swift
//
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// FeedFetchedResultsController.swift
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// FeedFetchedResultsController
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//
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// Created by Cirno MainasuK on 2021-8-19.
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// Copyright © 2021 Twidere. All rights reserved.
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//
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import os.log
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import Foundation
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import UIKit
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import Combine
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import CoreData
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import CoreDataStack
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import MastodonSDK
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final public class FeedFetchedResultsController: NSObject {
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public let logger = Logger(subsystem: "FeedFetchedResultsController", category: "DB")
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var disposeBag = Set<AnyCancellable>()
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public let fetchedResultsController: NSFetchedResultsController<Feed>
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// input
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@Published public var predicate = Feed.predicate(kind: .none, acct: .none)
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// output
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private let _objectIDs = PassthroughSubject<[NSManagedObjectID], Never>()
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@Published public var records: [ManagedObjectRecord<Feed>] = []
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public init(managedObjectContext: NSManagedObjectContext) {
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self.fetchedResultsController = {
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let fetchRequest = Feed.sortedFetchRequest
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// make sure initial query return empty results
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fetchRequest.returnsObjectsAsFaults = false
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fetchRequest.shouldRefreshRefetchedObjects = true
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fetchRequest.fetchBatchSize = 15
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let controller = NSFetchedResultsController(
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fetchRequest: fetchRequest,
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managedObjectContext: managedObjectContext,
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sectionNameKeyPath: nil,
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cacheName: nil
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)
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return controller
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}()
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super.init()
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// debounce output to prevent UI update issues
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_objectIDs
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.throttle(for: 0.1, scheduler: DispatchQueue.main, latest: true)
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.map { objectIDs in objectIDs.map { ManagedObjectRecord(objectID: $0) } }
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.assign(to: &$records)
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fetchedResultsController.delegate = self
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$predicate
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.removeDuplicates()
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.receive(on: DispatchQueue.main)
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.sink { [weak self] predicate in
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guard let self = self else { return }
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self.fetchedResultsController.fetchRequest.predicate = predicate
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do {
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try self.fetchedResultsController.performFetch()
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} catch {
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assertionFailure(error.localizedDescription)
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}
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}
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.store(in: &disposeBag)
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}
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deinit {
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logger.log(level: .debug, "\((#file as NSString).lastPathComponent, privacy: .public)[\(#line, privacy: .public)], \(#function, privacy: .public)")
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}
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}
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// MARK: - NSFetchedResultsControllerDelegate
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extension FeedFetchedResultsController: NSFetchedResultsControllerDelegate {
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public func controller(
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_ controller: NSFetchedResultsController<NSFetchRequestResult>,
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didChangeContentWith snapshot: NSDiffableDataSourceSnapshotReference
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) {
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os_log("%{public}s[%{public}ld], %{public}s", ((#file as NSString).lastPathComponent), #line, #function)
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let snapshot = snapshot as NSDiffableDataSourceSnapshot<String, NSManagedObjectID>
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self._objectIDs.send(snapshot.itemIdentifiers)
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}
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}
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