mastodon-app-ufficiale-ipho.../MastodonSDK/Sources/MastodonCore/FetchedResultsController/FeedFetchedResultsControlle...

99 lines
3.3 KiB
Swift

//
// FeedFetchedResultsController.swift
// FeedFetchedResultsController
//
// Created by Cirno MainasuK on 2021-8-19.
// Copyright © 2021 Twidere. All rights reserved.
//
import os.log
import Foundation
import UIKit
import Combine
import CoreData
import CoreDataStack
import MastodonSDK
final public class FeedFetchedResultsController: NSObject {
private enum Constants {
static let defaultFetchLimit = 100
}
public let logger = Logger(subsystem: "FeedFetchedResultsController", category: "DB")
var disposeBag = Set<AnyCancellable>()
private let fetchedResultsController: NSFetchedResultsController<Feed>
public var managedObjectContext: NSManagedObjectContext {
fetchedResultsController.managedObjectContext
}
// input
@Published public var predicate = Feed.predicate(kind: .none, acct: .none)
// output
private let _objectIDs = PassthroughSubject<[NSManagedObjectID], Never>()
@Published public var records: [ManagedObjectRecord<Feed>] = []
public func fetchNextBatch() {
fetchedResultsController.fetchRequest.fetchLimit += Constants.defaultFetchLimit
try? fetchedResultsController.performFetch()
}
public init(managedObjectContext: NSManagedObjectContext) {
self.fetchedResultsController = {
let fetchRequest = Feed.sortedFetchRequest
// make sure initial query return empty results
fetchRequest.returnsObjectsAsFaults = false
fetchRequest.shouldRefreshRefetchedObjects = true
fetchRequest.fetchBatchSize = 15
fetchRequest.fetchLimit = Constants.defaultFetchLimit
let controller = NSFetchedResultsController(
fetchRequest: fetchRequest,
managedObjectContext: managedObjectContext,
sectionNameKeyPath: nil,
cacheName: nil
)
return controller
}()
super.init()
// debounce output to prevent UI update issues
_objectIDs
.throttle(for: 0.1, scheduler: DispatchQueue.main, latest: true)
.map { objectIDs in objectIDs.map { ManagedObjectRecord(objectID: $0) } }
.assign(to: &$records)
fetchedResultsController.delegate = self
$predicate
.removeDuplicates()
.receive(on: DispatchQueue.main)
.sink { [weak self] predicate in
guard let self = self else { return }
self.fetchedResultsController.fetchRequest.predicate = predicate
do {
try self.fetchedResultsController.performFetch()
} catch {
assertionFailure(error.localizedDescription)
}
}
.store(in: &disposeBag)
}
}
// MARK: - NSFetchedResultsControllerDelegate
extension FeedFetchedResultsController: NSFetchedResultsControllerDelegate {
public func controller(
_ controller: NSFetchedResultsController<NSFetchRequestResult>,
didChangeContentWith snapshot: NSDiffableDataSourceSnapshotReference
) {
let snapshot = snapshot as NSDiffableDataSourceSnapshot<String, NSManagedObjectID>
self._objectIDs.send(snapshot.itemIdentifiers)
}
}