Observe call from Firebase not updating value of dictionary after function exit - ios

Question

I'm trying to learn iOS programming so I thought it would be a good idea to emulate instagrams feed. Everyone uses this basic feed and I would like to know how to do it.
The basic idea is to have one image/text post show up in a single column. Right now I have a a single image to be shown.
I'm currently extracting the image url correctly from firebase. The only issue is that my CollectionView still is showing up empty. I started this project months ago and I forget where the tutorial is at. Please help me fill in the blanks. Here is the code:
import UIKit
import SwiftUI
import Firebase
import FirebaseUI
import SwiftKeychainWrapper
class FeedViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource{
#IBOutlet weak var collectionview: UICollectionView!
//var posts = [Post]()
var posts = [String](){
didSet{
collectionview.reloadData()
}
}
var following = [String]()
var posts1 = [String]()
var userStorage: StorageReference!
var ref : DatabaseReference!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
posts1 = fetchPosts()
//let myIndexPath = IndexPath(row: 0, section: 0)
//collectionView(collectionview, cellForItemAt: myIndexPath)
//print(self.posts1.count)
}
func fetchPosts() -> [String]{
let uid = Auth.auth().currentUser!.uid
let ref = Database.database().reference().child("posts")
let uids = Database.database().reference().child("users")
uids.observe(DataEventType.value, with: { (snapshot) in
let dict = snapshot.value as! [String:NSDictionary]
for (_,value) in dict {
if let uid = value["uid"] as? String{
self.following.append(uid)
}
}
ref.observe(DataEventType.value, with: { (snapshot2) in
let dict2 = snapshot2.value as! [String:NSDictionary]
for(key, value) in dict{
for uid2 in self.following{
if (uid2 == key){
for (key2,value2) in value as! [String:String]{
//print(key2 + "this is key2")
if(key2 == "urlToImage"){
let urlimage = value2
//print(urlimage)
self.posts1.append(urlimage)
self.collectionview.reloadData()
print(self.posts1.count)
}
}
}
}
}
})
})
//ref.removeAllObservers()
//uids.removeAllObservers()
print("before return")
print(self.posts1.count)
return self.posts1
override func viewDidLayoutSubviews() {
collectionview.reloadData()
}
func numberOfSections(in collectionView: UICollectionView) ->Int {
return 1
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return posts1.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "PostCell", for: indexPath) as! PostCell
cell.postImage.sd_setImage(with: URL(string: posts1[indexPath.row]))
//creating the cell
//cell.postImage.downloadImage(from: self.posts[indexPath.row])
// let storageRef = Storage.storage().reference(forURL: self.posts[indexPath.row].pathToImage)
//
//
print("im trying")
//let stickitinme = URL(fileURLWithPath: posts1[0])
//cell.postImage.sd_setImage(with: stickitinme)
//cell.authorLabel.text = self.posts[indexPath.row].author
//cell.likeLabel.text = "\(self.posts[indexPath.row].likes) Likes"
return cell
}
#IBAction func signOutPressed(_sender: Any){
signOut()
self.performSegue(withIdentifier: "toSignIn", sender: nil)
}
#objc func signOut(){
KeychainWrapper.standard.removeObject(forKey:"uid")
do{
try Auth.auth().signOut()
} catch let signOutError as NSError{
print("Error signing out: %#", signOutError)
}
dismiss(animated: true, completion: nil)
}
/*
// MARK: - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
// Get the new view controller using segue.destination.
// Pass the selected object to the new view controller.
}
*/
}
UPDATE
The observe call is not updating the value of posts (the dictionary). Once the observe call exits, the value of posts is set back to empty.
PostCell class as asked:
import UIKit
class PostCell: UICollectionViewCell {
#IBOutlet weak var postImage: UIImageView!
#IBOutlet weak var authorLabel: UILabel!
#IBOutlet weak var likeLabel:UILabel!
#IBOutlet weak var likeBtn:UIButton!
#IBOutlet weak var unlikeBtn:UIButton!
#IBAction func likePressed (_ sender: Any){
}
#IBAction func unlikePressed(_sender: Any){
}
}

Answer 1

I think the problem is:
Your collectionView dataSource is called only once. Since the image url loading is asynchronous, you will need to refresh your collectionview every time new data is appended to your datasource array like this:
self.posts.append(urlimage)
collectionView.reloadData()
or:
var posts = [UIImage](){
didSet{
collectionView.reloadData()
}
}
Hope this helps.
Edit update:
Regarding the asynchronous calls, i think you should use escaping closure that runs the code block once the network request receives a response.
First separate the network call functions like:
func fetchUsers(completion: #escaping(_ dictionary: [String: NSDictionary])->()){
let uid = Auth.auth().currentUser!.uid
let uids = Database.database().reference().child("users")
uids.observe(DataEventType.value, with: { (snapshot) in
let dict = snapshot.value as! [String:NSDictionary]
completion(dict)
})
}
func fetchURLS(completion: #escaping(_ dictionary: [String: String])->()){
let ref = Database.database().reference().child("posts")
ref.observe(DataEventType.value, with: { (snapshot2) in
let dict2 = snapshot2.value as! [String:String]
completionTwo(dict2)
})
}
Then, the parsing functions:
func parseUsers(dictionary: [String: NSDictionary]){
for (_,value) in dictionary {
if let uid = value["uid"] as? String{
self.following.append(uid)
}
}
fetchURLS { (urlDictionary) in
self.parseImageURLS(dictionary: urlDictionary)
}
}
func parseImageURLS(dictionary: [String: String]){
for(key, value) in dictionary{
for uid2 in self.following{
if (uid2 == key){
for (key2,value2) in value as! [String:String]{
//print(key2 + "this is key2")
if(key2 == "urlToImage"){
let urlimage = value2
//print(urlimage)
self.posts1.append(urlimage)
self.collectionview.reloadData()
print(self.posts1.count)
}
}
}
}
}
}
Then you add:
fetchUsers { (usersDictionary) in
self.parseUsers(dictionary: usersDictionary)
}
in viewDidLoad()
Hope this solves your problem. On a side note: I recommend using models and separating the network calls in a different file. Feel free to ask any questions.

Answer 2

I figured out how to do it after more searching.
I was incorrectly assuming that the CollectionView is loaded after the viewDidLoad() function is done. The helper classes for a CollectionView are called to a call of reloadData.
I observed that my reloadData call wasn't being called. In order to make this work, I add 2 lines of code to the viewDidLoad function:
collectionview.delegate = self
collectionview.dataSource = self
With this change, the images now load.