Cells won't load when using multiple collection views - swift

Question

I have two collection views that get their data from two arrays that append from a url session function. I deleted everything and started over and I get that same problem. I added a breakpoint and the arrays are getting filled. I also saw on other solutions, reloadData() was used after the array is filled but doesn't work for me
HomeViewController:
//Variable declarations
var recentlyPlayed = [RecentlyPlayed]()
private var info = UserDefaults.standard.dictionary(forKey: "parseJSON")
var userLikedSongs = [LikedSongs]()
var refreshControl: UIRefreshControl!
#IBOutlet weak var LikedSongsCollectionView: UICollectionView!
#IBOutlet weak var RecentlyPlayedCollectionView: UICollectionView!
#IBOutlet weak var scrollView: UIScrollView!
//Once view has loaded
override func viewDidLoad() {
super.viewDidLoad()
//Assign Collection views to self
RecentlyPlayedCollectionView.delegate = self
RecentlyPlayedCollectionView.dataSource = self
LikedSongsCollectionView.delegate = self
LikedSongsCollectionView.dataSource = self
// Get user id and users recently played songs
let user = getId()
let id = Int(user)!
retriveRecentSongs(info: id)
retriveLikedSongs(info: id)
RecentlyPlayedCollectionView.reloadData()
LikedSongsCollectionView.reloadData()
//Hide navigation bar
self.navigationController?.isNavigationBarHidden = true
}
// Define Recent songs collection view count
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
if(collectionView == RecentlyPlayedCollectionView) {
return recentlyPlayed.count
} else {
return userLikedSongs.count
}
}
//Set content inside recently collection view cells
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell{
if (collectionView == LikedSongsCollectionView) {
let likeCell = collectionView.dequeueReusableCell(withReuseIdentifier: "LikedCell", for: indexPath) as! LikedSongsCollectionViewCell
likeCell.LikedData = userLikedSongs[indexPath.row]
return likeCell
} else {
let recentCell = collectionView.dequeueReusableCell(withReuseIdentifier: "RecentlyPlayedCell", for: indexPath) as! RecentlyPlayedCollectionViewCell
recentCell.Recentdata = recentlyPlayed[indexPath.row]
return recentCell
}
}
//Get users recenlty played song with URL session
func retriveRecentSongs(info: Int) {
let url = URL(string: "http://127.0.0.1/musicfiles/getRecentlyPlayed.php?info=" + String(info))
URLSession.shared.dataTask(with: url!) { data, response, error in
let retrievedList = String(data: data!, encoding: String.Encoding.utf8)
print(retrievedList!)
self.parseRecentSongs(data: retrievedList!)
}
.resume()
print("Getting songs")
}
func parseRecentSongs (data: String) {
if (data.contains("*")) {
let dataArray = (data as String).split(separator: "*").map(String.init)
for item in dataArray {
let itemData = item.split(separator: ",").map(String.init)
let newSong = RecentlyPlayed(id: itemData[0], songName: itemData[1], trackName: itemData[2], artist: itemData[3], owner: itemData[4], cover: itemData[5])
recentlyPlayed.append(newSong)
}
}
}
Also can add RecentlyPlayedCollectionViewCell and LikedSongsCollectionView if needed.

Answer 1

Your function retriveRecentSongs contains an asynchronous closure. That means code inside it continues to execute even after it's called and returned.
func retriveRecentSongs(info: Int) {
let url = URL(string: "http://127.0.0.1/musicfiles/getRecentlyPlayed.php?info=" + String(info))
/// See here!
URLSession.shared.dataTask(with: url!) { data, response, error in
let retrievedList = String(data: data!, encoding: String.Encoding.utf8)
print(retrievedList!)
self.parseRecentSongs(data: retrievedList!)
}
.resume()
print("Getting songs")
}
You might notice how print("Getting songs") is printed before print(retrievedList!).
When "Getting songs" is printed, you've only just started the URL task, and the download hasn't completed yet. At this point, recentlyPlayed is still empty.
retriveRecentSongs(info: id) /// started the download
RecentlyPlayedCollectionView.reloadData() /// but at this point, has not completed yet.
You need to call reloadData once the download has finished.
func retriveRecentSongs(info: Int) {
let url = URL(string: "http://127.0.0.1/musicfiles/getRecentlyPlayed.php?info=" + String(info))
URLSession.shared.dataTask(with: url!) { data, response, error in
let retrievedList = String(data: data!, encoding: String.Encoding.utf8)
print(retrievedList!)
/// ok, the download finished, parse the songs
self.parseRecentSongs(data: retrievedList!)
}
.resume()
print("Getting songs")
}
func parseRecentSongs (data: String) {
if (data.contains("*")) {
let dataArray = (data as String).split(separator: "*").map(String.init)
for item in dataArray {
let itemData = item.split(separator: ",").map(String.init)
let newSong = RecentlyPlayed(id: itemData[0], songName: itemData[1], trackName: itemData[2], artist: itemData[3], owner: itemData[4], cover: itemData[5])
recentlyPlayed.append(newSong)
}
}
/// now, do reloadData.
RecentlyPlayedCollectionView.reloadData()
}
Also make sure you delete
RecentlyPlayedCollectionView.reloadData()
LikedSongsCollectionView.reloadData()
inside viewDidLoad().