How to load image from Firebase into users avatar - swift

Question

I have a problem with loading images from firebase. I have two functions. One of them collect info about user, second one load users avatar image. Unfortunately images load after function creates new user. I know it will be problem with asynchronous of Firebase but I don't know how to set up DispatchQueue to work properly. Can you help me with that?
// function that load user image in user manager class
func loadUserImage(contactUserID: String, completion: #escaping (UIImage) -> Void) {
let userID = Auth.auth().currentUser!.uid
var userImageRef = self.storage.child("\(userID)/userImage.jpg")
var image = UIImage()
if contactUserID != "" {
userImageRef = self.storage.child("\(contactUserID)/userImage.jpg")
}
userImageRef.getData(maxSize: 5 * 1024 * 1024) { (data, error) in
if let error = error {
print("Error with retrieving data: \(error.localizedDescription)")
} else {
if data?.count != 0 {
image = UIImage(data: data!)!
} else {
image = UIImage(systemName: "person.circle.fill")!
}
completion(image)
}
}
}
// function that load user in contact manager class
func loadContactList(completion: #escaping ([User]) -> Void) {
let currentUserID = Auth.auth().currentUser!.uid
db.collection("contacts")
.document(currentUserID)
.collection("userContacts")
.addSnapshotListener { (querySnapshot, error) in
var contactList = [User]()
if let error = error {
print("Error with retrieving data from DB: \(error.localizedDescription)")
} else {
if let snapshotDocuments = querySnapshot?.documents {
for document in snapshotDocuments {
let data = document.data()
let uid = data["uid"] as! String
let name = data["name"] as! String
let email = data["email"] as! String
var contact = User(email: email, name: name, userID: uid)
DispatchQueue.global().sync {
self.userService.loadUserImage(contactUserID: uid) { (image) in
contact.photoURL = image
}
}
contactList.append(contact)
contactList.sort {
$0.name < $1.name
}
completion(contactList)
}
}
}
}
}
// Function implementation in viewController
func loadContactList() {
self.contactService.loadContactList { (contactArray) in
self.contactList = contactArray
self.tableView.reloadData()
}
}

Answer 1

What you can do is to store the image url in the firebase database and after that create this extension:
import UIKit
let imageCache: NSCache = NSCache<AnyObject, AnyObject>()
extension UIImageView {
func loadImageUsingCacheWithUrlString(urlString: String) {
self.image = nil
if let cachedImage = imageCache.object(forKey: urlString as AnyObject) as? UIImage {
self.image = cachedImage
return
}
let url = URL(string: urlString)
if let data = try? Data(contentsOf: url!) {
DispatchQueue.main.async(execute: {
if let downloadedImage = UIImage(data: data) {
imageCache.setObject(downloadedImage, forKey: urlString as AnyObject)
self.image = downloadedImage
}
})
}
}
}
And call:
if let url = data["imgUrl"] as? String {
self.myImageView.loadImageUsingCacheWithUrlString(urlString: url)
}
For that what you need to do is to create and initialize an UIImage object. If you are working with cell classes you need to create this object in the cell.