mastodon-ios/Mastodon/Diffiable/FetchedResultsController/SearchHistoryFetchedResultC...

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//
// SearchHistoryFetchedResultController.swift
// Mastodon
//
// Created by MainasuK Cirno on 2021-7-15.
//
import os.log
import UIKit
import Combine
import CoreData
import CoreDataStack
import MastodonSDK
final class SearchHistoryFetchedResultController: NSObject {
var disposeBag = Set<AnyCancellable>()
let fetchedResultsController: NSFetchedResultsController<SearchHistory>
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let domain = CurrentValueSubject<String?, Never>(nil)
let userID = CurrentValueSubject<Mastodon.Entity.Status.ID?, Never>(nil)
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// output
let _objectIDs = CurrentValueSubject<[NSManagedObjectID], Never>([])
@Published var records: [ManagedObjectRecord<SearchHistory>] = []
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init(managedObjectContext: NSManagedObjectContext) {
self.fetchedResultsController = {
let fetchRequest = SearchHistory.sortedFetchRequest
fetchRequest.returnsObjectsAsFaults = false
fetchRequest.fetchBatchSize = 20
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)
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fetchedResultsController.delegate = self
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Publishers.CombineLatest(
self.domain,
self.userID
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)
.receive(on: DispatchQueue.main)
.sink { [weak self] domain, userID in
guard let self = self else { return }
let predicates = [SearchHistory.predicate(domain: domain ?? "", userID: userID ?? "")]
self.fetchedResultsController.fetchRequest.predicate = NSCompoundPredicate(andPredicateWithSubpredicates: predicates)
do {
try self.fetchedResultsController.performFetch()
} catch {
assertionFailure(error.localizedDescription)
}
}
.store(in: &disposeBag)
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}
}
// MARK: - NSFetchedResultsControllerDelegate
extension SearchHistoryFetchedResultController: NSFetchedResultsControllerDelegate {
func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeContentWith snapshot: NSDiffableDataSourceSnapshotReference) {
os_log("%{public}s[%{public}ld], %{public}s", ((#file as NSString).lastPathComponent), #line, #function)
let objects = fetchedResultsController.fetchedObjects ?? []
self._objectIDs.value = objects.map { $0.objectID }
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}
}