现在我要做我的RSSReader应用程序，需要在其上添加CoreData。 我使用pod FeedKit，它具有RSSFeed类，该类从chanel接收数据。我需要将该数据保存到CoreData，然后显示在我的应用程序上。我有一个DataManager，它具有CoreData中的saveChanel方法。
我在DataManager上获得的数据。 DataManager具有方法loadChanel，该方法具有来自CoreData的方法saveChanel（PersistanceManager.shared.saveChanell（feed：RSSFeed））。 我的coreDataModel有2个实体“ Item”和“ Chanel”。
我知道我在PersistanceManager上的代码中有问题（下面的代码）。有人可以帮忙吗？
我的DataManager是：
class DataManager {
static let sharedInstance = DataManager()
// var dataManagerDelegate: DataManagerDelegate?
var myLinkString: String!
private init() {}
// MARK: - Public
func loadChanel(completion: @escaping ([Chanel]?, Error?, Bool) -> Void, channelAddres: String) {
guard let myLink = myLinkString, let linkUrl = URL(string: myLink) else { return }
let parser = FeedParser(URL: linkUrl)
let result = parser.parse()
guard let feed = result.rssFeed, result.isSuccess else { return }
PersistanceManager.shared.saveChanell(feed: RSSFeed)
}
func loadChannels(completion: @escaping ([Chanel]?, Error?, Bool) -> Void) {
func performCompletion(channels: [Chanel]?, error: Error?, finished: Bool) {
DispatchQueue.main.async {
completion(channels, error, finished)
}
}
/*
* Fetch local channels
*/
let cachedChannels = PersistanceManager.shared.fetchRssChannels()
performCompletion(channels: cachedChannels, error: nil, finished: false)
/*
* Load channels from server
*/
myLinkString = "https://..."
guard let linkUrl = URL(string: myLinkString) else { return }
let parser = FeedParser(URL: linkUrl)
let result = parser.parse()
guard let feed = result.rssFeed, result.isSuccess else { return }
/*
* Store data to database
*/
PersistanceManager.shared.saveChanell(channel: Chanel, feed: RSSFeed)
/*
* Get actual posts from data base and return
*/
let updatedChannels = PersistanceManager.shared.fetchRssChannels()
performCompletion(channels: updatedChannels, error: nil, finished: true)
}
func saveContext() {
PersistanceManager.shared.saveContext()
}
}
在DataManager上，以下几行出现3个错误：
PersistanceManager.shared.saveChanell(feed: RSSFeed)
PersistanceManager.shared.saveChanell(channel: Chanel, feed: RSSFeed)
错误是： “无法将类型'RSSFeed.Type'的值转换为预期的参数类型'RSSFeed'”）； “无法将类型“ Chanel.Type”的值转换为预期的参数类型“ Chanel””
和PersistanceManager：
import Foundation
import CoreData
import FeedKit
class PersistanceManager {
// wrapper for core data
static var shared = PersistanceManager()
private init() {}
func saveChanell(feed: RSSFeed) {
let channel = createNewChanel(with: feed.title)
channel?.rssDescription = feed.description
channel?.pubdate = feed.pubDate! as NSDate
channel?.link = feed.link
channel?.language = feed.language
channel?.creator = feed.dublinCore?.dcCreator
guard let feedItems = feed.items else {
return
}
guard let _ = channel?.item else {
channel?.item = NSSet()
}
guard let channelItems = channel?.item else {
return
}
for feedItem in feedItems {
}
// 5
do {
try context.save()
print("Channel saved")
} catch {}
}
func saveChanell(channel: Chanel, feed: RSSFeed) {
channel.title = feed.title
channel.rssDescription = feed.description
channel.pubdate = feed.pubDate! as NSDate
//channel.pubDate = NSDate(timeIntervalSince1970: feed.pubDate?.timeIntervalSince1970)
channel.link = feed.link
channel.language = feed.language
//channel.isLastUsed
channel.creator = feed.dublinCore?.dcCreator
guard let items = feed.items else {
return
}
// 3
for item in items {
guard let mediaLink = item.media?.mediaThumbnails?.first?.attributes?.url else {
continue
}
let rssItem = createRssItem(with: mediaLink, in: context)
rssItem?.title = item.title
// rssItem?.pubdate = (item.pubDate as! NSDate)
rssItem?.link = item.link
rssItem?.itemDescription = item.description
rssItem?.category = item.categories?.first?.value
channel.item?.adding(rssItem as Any)
}
// 5
do {
try context.save()
print("Channel saved")
} catch {}
}
// 4
private func createRssItem(with mediaLink: String, in context: NSManagedObjectContext) -> Item? {
let newRssItem = NSEntityDescription.insertNewObject(forEntityName: "Item", into: context) as? Item
newRssItem?.mediaLink = mediaLink
print("RSS Item created")
return newRssItem
}
func fetchRssChannels() -> [Chanel]? {
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Chanel")
do {
let channels = try self.context.fetch(fetchRequest) as? [Chanel]
return channels
} catch let error {
print(error)
}
print("RSS channels fetched")
return nil
}
// 2 - а тот ли тут канал
func createNewChanel(with chanel: Chanel) -> Chanel? {
if let findRssChannelCD = findRssChannel(title: chanel.title) {
print("findRssChannelCD")
return findRssChannelCD
}
let newRssChannelCD = NSEntityDescription.insertNewObject(forEntityName: "Chanel", into: context) as? Chanel
newRssChannelCD?.title = chanel.title
newRssChannelCD?.item = NSSet()
do {
try context.save()
print("newChanelSaved")
} catch {}
return newRssChannelCD
}
// 1
private func findRssChannel(title: String?) -> Chanel? {
guard let title = title else {
return nil
}
let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Chanel")
request.predicate = NSPredicate(format: "title = %@", title)
do {
let users = try context.fetch(request) as? [Chanel]
return users?.first
} catch {}
return nil
}
// MARK: - Core Data stack
var context: NSManagedObjectContext {
return persistentContainer.viewContext
}
lazy var persistentContainer: NSPersistentContainer = {
/*
The persistent container for the application. This implementation
creates and returns a container, having loaded the store for the
application to it. This property is optional since there are legitimate
error conditions that could cause the creation of the store to fail.
*/
let container = NSPersistentContainer(name: "NewsForIphone")
container.loadPersistentStores(completionHandler: { (_, error) in
if let error = error as NSError? {
// Replace this implementation with code to handle the error appropriately.
// fatalError() causes the application to generate a crash log and terminate.
//You should not use this function in a shipping application, although it may be useful during development.
/*
Typical reasons for an error here include:
* The parent directory does not exist, cannot be created, or disallows writing.
* The persistent store is not accessible, due to permissions or data protection when the device is locked.
* The device is out of space.
* The store could not be migrated to the current model version.
Check the error message to determine what the actual problem was.
*/
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
return container
}()
// MARK: - Core Data Saving support
public func saveContext () {
let context = persistentContainer.viewContext
if context.hasChanges {
do {
try context.save()
} catch {
// Replace this implementation with code to handle the error appropriately.
// fatalError() causes the application to generate a crash log and terminate.
//You should not use this function in a shipping application, although it may be useful during development.
let nserror = error as NSError
fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
}
}
}
}
我知道我在PersistanceManager上的代码中有问题（下面的代码），并且在DataManager中有错误。有人可以帮忙吗？
答案 0 :(得分：0)
问题是由以下行引起的：
PersistanceManager.shared.saveChanell(feed: RSSFeed)
您要指定实际的类名而不是对象，您需要编写：
PersistanceManager.shared.saveChanell(feed: feed)