我正在学习iOS swift并创建一个应用程序，以便在使用Itunes搜索API时学习获取JSON数据并将此数据保存到CoreData。我有一个表视图，并使用自定义表视图单元格，它有一些标签，图像和下载按钮。我的目的是能够在单击单元格按钮后将专辑和该专辑信息中的所有歌曲输入CoreData。以下列出了有效和无效的内容：
代码： API控制器获取歌曲信息。
import Foundation
protocol songAPIControllerForCoreDataProtocol {
func didReceiveAPISongResults(results: NSDictionary)
}
class songAPIControllerForCoreData {
var delegate: songAPIControllerForCoreDataProtocol
init(delegate: songAPIControllerForCoreDataProtocol) {
self.delegate = delegate
}
func searchItunesForSongsBelongingTo(searchTerm: String) {
// The iTunes API wants multiple terms separated by + symbols, so I'm replacing spaces with + signs
let itunesSearchTerm = searchTerm.stringByReplacingOccurrencesOfString(" ", withString: "+", options: NSStringCompareOptions.CaseInsensitiveSearch, range: nil)
// Escape anything else that isn't URL-friendly
if let escapedSearchTerm = itunesSearchTerm.stringByAddingPercentEscapesUsingEncoding(NSUTF8StringEncoding) {
// Using Itunes search api to find people that has a music album with the entered search term
let urlPath = "https://itunes.apple.com/lookup?id=\(escapedSearchTerm)&entity=song"
let url: NSURL = NSURL(string: urlPath)!
let session = NSURLSession.sharedSession()
let task = session.dataTaskWithURL(url, completionHandler: {data, response, error -> Void in
println("Task completed")
if(error != nil) {
// If there is an error in the web request, print it to the console
println(error.localizedDescription)
}
var err: NSError?
var jsonResult = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: &err) as! NSDictionary
println(jsonResult[0])
if(err != nil) {
// If there is an error parsing JSON, print it to the console
println("JSON Error \(err!.localizedDescription)")
}
self.delegate.didReceiveAPISongResults(jsonResult)
println(jsonResult)
})
task.resume()
}
}
}
Song class（非CoreData）：
import Foundation
class Song {
var title: String
var previewURL: String
var collectionID: Int
init(title: String, previewURL: String, collectionID: Int) {
self.title = title
self.previewURL = previewURL
self.collectionID = collectionID
}
class func songsWithJSON(allResults: NSArray) -> [Song] {
// Create an empty array of Albums to append to from this list
var songs = [Song]()
// Store the results in our table data array
if allResults.count>0 {
// Sometimes iTunes returns a collection, not a track, so we check both for the 'name'
for result in allResults {
var title = result["trackName"] as? String
if title == nil {
title = result["collectionName"] as? String
}
if title == nil {
title = result["collectionName"] as? String
}
let previewURL = result["previewUrl"] as? String ?? ""
let collectionID = result["collectionId"] as? Int ?? 0
var newSong = Song(title: title!, previewURL: previewURL, collectionID: collectionID)
songs.append(newSong)
}
}
return songs
}
}
最后是AlbumViewController：
import UIKit
import CoreData
class AlbumViewController: UIViewController, UITableViewDelegate, UITableViewDataSource, searchAPIControllerProtocol, songAPIControllerForCoreDataProtocol {
@IBOutlet
var tableView: UITableView!
@IBOutlet weak var artistNameOutlet: UILabel!
var songapi : songAPIControllerForCoreData?
var api : searchAPIController?
var albums = [Album]()
var songs = [Song]()
var imageCache = [String : UIImage]()
//Variables that take the values after segue from uTableViewController
var artistID, artistName: String?
let cellIdentifier: String = "albumCell"
//for CoreData
var error:NSError?
let managedObjectContext = (UIApplication.sharedApplication().delegate
as! AppDelegate).managedObjectContext
func numberOfSectionsInTableView(tableView: UITableView) -> Int {
// #warning Potentially incomplete method implementation.
// Return the number of sections.
return 1
}
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return self.albums.count
}
func download(sender: AnyObject){
var senderButton : UIButton = sender as! UIButton
let newAlbum = NSEntityDescription.insertNewObjectForEntityForName("Albums", inManagedObjectContext: managedObjectContext!) as! Albums
let newSong = NSEntityDescription.insertNewObjectForEntityForName("Songs", inManagedObjectContext: managedObjectContext!) as! Songs
songapi!.searchItunesForSongsBelongingTo((String)(self.albums[senderButton.tag].collectionID))
newAlbum.albumArt = self.albums[senderButton.tag].largeImageURL
newAlbum.albumID = (String)(self.albums[senderButton.tag].collectionID)
newAlbum.albumName = self.albums[senderButton.tag].title
newAlbum.albumPrice = self.albums[senderButton.tag].price
newAlbum.artistID = self.artistID!
newAlbum.artistName = self.artistName!
newAlbum.numberOfSongs = (String)(self.albums[senderButton.tag].trackCount)
newAlbum.has = []
println(self.songs)
for(var i = 1; i < self.albums[senderButton.tag].trackCount - 1; i++){
newSong.collectionID = String(self.songs[i].collectionID)
newSong.previewURL = self.songs[i].previewURL
newSong.songName = self.songs[i].title
}
self.managedObjectContext?.save(&self.error)
println(newAlbum)
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell: AlbumTableViewCell = tableView.dequeueReusableCellWithIdentifier(cellIdentifier) as! AlbumTableViewCell
cell.albumCellButton.tag = indexPath.row
cell.albumCellButton.addTarget(self, action: "download:", forControlEvents: .TouchUpInside)
let album = self.albums[indexPath.row]
cell.albumName.text = album.title
cell.artistImage.image = UIImage(named: "user7.png")
cell.numberOfSongs.text = (String)(album.trackCount) + " Songs"
// Get the formatted price string for display in the subtitle
let formattedPrice = album.price
// Grab the artworkUrl60 key to get an image URL for the app's thumbnail
let urlString = album.thumbnailImageURL
// Check our image cache for the existing key. This is just a dictionary of UIImages
var image = self.imageCache[urlString]
if( image == nil ) {
// If the image does not exist, we need to download it
var imgURL: NSURL = NSURL(string: urlString)!
// Download an NSData representation of the image at the URL
let request: NSURLRequest = NSURLRequest(URL: imgURL)
NSURLConnection.sendAsynchronousRequest(request, queue: NSOperationQueue.mainQueue(), completionHandler: {(response: NSURLResponse!,data: NSData!,error: NSError!) -> Void in
if error == nil {
image = UIImage(data: data)
// Store the image in to our cache
self.imageCache[urlString] = image
dispatch_async(dispatch_get_main_queue(), {
if let cellToUpdate = tableView.cellForRowAtIndexPath(indexPath) as?AlbumTableViewCell {
cellToUpdate.artistImage.image = image
}
})
}
else {
println("Error: \(error.localizedDescription)")
}
})
}
else {
dispatch_async(dispatch_get_main_queue(), {
if let cellToUpdate = tableView.cellForRowAtIndexPath(indexPath) as?AlbumTableViewCell {
cellToUpdate.artistImage.image = image
}
})
}
cell.priceOfAlbum.text = formattedPrice
return cell
}
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
}
func didReceiveAPIResults(results: NSDictionary) {
var resultsArr: NSArray = results["results"] as! NSArray
dispatch_async(dispatch_get_main_queue(), {
self.albums = Album.albumsWithJSON(resultsArr)
self.tableView!.reloadData()
UIApplication.sharedApplication().networkActivityIndicatorVisible = false
})
}
func didReceiveAPISongResults(results: NSDictionary) {
var resultsArr: NSArray = results["results"] as! NSArray
dispatch_async(dispatch_get_main_queue(), {
self.songs = Song.songsWithJSON(resultsArr)
self.tableView!.reloadData()
UIApplication.sharedApplication().networkActivityIndicatorVisible = false
})
}
override func viewDidLoad() {
super.viewDidLoad()
self.navigationItem.title = artistName
artistNameOutlet.text = " Albums"
api = searchAPIController(delegate: self)
songapi = songAPIControllerForCoreData(delegate: self)
UIApplication.sharedApplication().networkActivityIndicatorVisible = true
api!.searchItunesForAlbumsBelongingTo(self.artistName!, id: self.artistID!)
// Do any additional setup after loading the view.
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
let songsController = segue.destinationViewController as! SongsViewController
var albumCollectionID = self.albums
var albumIndex = tableView!.indexPathForSelectedRow()!.row
var collectionID = self.albums[albumIndex].collectionID
var albumName = self.albums[albumIndex].title
songsController.albumName = albumName
songsController.collectionID = collectionID
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
答案 0 :(得分：0)
您需要编写协议的定义，如下所示：
protocol songAPIControllerForCoreDataProtocol : class {
func didReceiveAPISongResults(results: NSDictionary)
}
这将使其成为仅类协议，并将强制确认类型具有引用语义。如果没有＆＃39; class＆＃39;指定了关键字，它将具有值语义。
没有＆＃39;班级＆＃39;关键字这里的问题我假设是通过初始化程序设置委托。当您传递委托时：
songapi = songAPIControllerForCoreData(delegate: self)
这将假定委托参数为值类型并复制值而不是发送它的引用。因此，当您在init（）中设置该值时，委托成员将指向一个新对象，而不是传递给UIViewController。
如果您将代理设置为：
songapi.delegate = self
它可以在没有＆＃39;类的情况下工作。协议定义中的关键字。