Delay on load screen objects - ios

Question

I don't know why but when I open the app, it takes a while to load all the data on the screen, until there remains a white screen without content. All the data loaded is downloaded from an API. What should I do to make it better?
App Loaded after about 10 seconds:
I'll post below how I'm parsing all the data.
ViewController.swift:
import UIKit
class ViewController: UIViewController, UICollectionViewDataSource, UITableViewDataSource {
#IBOutlet weak var tableViewTopSell: UITableView!
#IBOutlet var collectionView: UICollectionView!
#IBOutlet weak var collectionViewBanner: UICollectionView!
var dataSource: [Content] = [Content]()
var dataBanner: [Banner] = [Banner]()
var dataTopSold: [Top10] = [Top10]()
override func viewDidLoad() {
super.viewDidLoad()
//SetupNavBarCustom
self.navigationController?.navigationBar.CustomNavigationBar()
let logo = UIImage(named: "tag.png")
let imageView = UIImageView(image:logo)
self.navigationItem.titleView = imageView
//CallAPIData
getTopSold { (data) in
DispatchQueue.main.async {
self.dataTopSold = data
self.tableViewTopSell.reloadData()
}
}
getBanner { (data) in
DispatchQueue.main.async {
self.dataBanner = data
self.collectionViewBanner.reloadData()
}
}
getAudiobooksAPI { (data) in
DispatchQueue.main.async {
self.dataSource = data
self.collectionView.reloadData()
}
}
}
//CollectionView
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
if (collectionView == self.collectionView) {
return self.dataSource.count
}else{
return self.dataBanner.count
}}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
if (collectionView == self.collectionView) {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "collectionViewCell", for: indexPath) as! CollectionViewCell
let content = self.dataSource[indexPath.item]
cell.bookLabel.text = content.descricao
cell.bookImage.setImage(url: content.urlImagem, placeholder: "")
return cell
}else if (collectionView == self.collectionViewBanner) {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "collectionViewCellBanner", for: indexPath) as! CollectionViewCell
let content = self.dataBanner[indexPath.item]
cell.bannerImage.setImage(url: content.urlImagem, placeholder: "")
return cell
}
return UICollectionViewCell()
}
//TableView
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return self.dataTopSold.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "topSoldCell", for: indexPath) as! TableViewCell
let content = self.dataTopSold[indexPath.item]
cell.labelNomeTopSell.text = content.nome
cell.imageViewTopSell.setImage(url: content.urlImagem, placeholder: "")
return cell
}
}
extension UIImageView{
func setImage(url : String, placeholder: String, callback : (() -> Void)? = nil){
self.image = UIImage(named: "no-photo")
URLSession.shared.dataTask(with: NSURL(string: url)! as URL, completionHandler: { (data, response, error) -> Void in
guard error == nil else{
return
}
DispatchQueue.main.async(execute: { () -> Void in
let image = UIImage(data: data!)
self.image = image
if let callback = callback{
callback()
}
})
}).resume()
}
}
DataStore.swift:
import Foundation
import UIKit
func getBanner(_ completion:#escaping ([Banner])->Void) {
let url = URL(string: "https://alodjinha.herokuapp.com/banner")
let session = URLSession.shared
guard let unwrappedURL = url else { print("Error unwrapping URL"); return }
let dataTask = session.dataTask(with: unwrappedURL) { (data, response, error) in
guard let unwrappedDAta = data else { print("Error unwrapping data"); return }
do {
let jsonBanner = try JSONDecoder().decode(BannerData.self, from: unwrappedDAta)
completion(jsonBanner.data)
} catch {
print("Could not get API data. \(error), \(error.localizedDescription)")
}
}
dataTask.resume()
}
func getTopSold(_completion:#escaping ([Top10])->Void) {
let url = URL(string: "https://alodjinha.herokuapp.com/produto/maisvendidos")
let session = URLSession.shared
guard let unwrappedURL = url else { print("Error url"); return}
let dataTask = session.dataTask(with: unwrappedURL) { (data, response, error) in
guard let unwrappedData = data else { print("Error data"); return}
do {
let jsonTop10 = try JSONDecoder().decode(Top10Data.self, from: unwrappedData)
_completion(jsonTop10.data)
}catch{
print("Could no get API data")
}
}
dataTask.resume()
}
Model.swift:
import Foundation
//Categorias
struct Contents : Decodable {
let data : [Content]
}
struct Content : Decodable {
let id : Int
let descricao : String
let urlImagem : String
}
//Banner
struct BannerData : Decodable {
let data : [Banner]
}
struct Banner : Decodable {
let id : Int
let urlImagem : String
let linkUrl : String
}
//Top10
struct Top10Data:Decodable {
let data: [Top10]
}
struct Top10:Decodable {
let id : Int
let nome : String
let urlImagem : String
}

Answer 1

Apart from it's a heavy network loading VC , you Currently don't have any problems loading the data as all are out of main thread , the only problem is loading the images as when you scroll it re-download the image again which may be just downloaded for this i recommend using SDWebImage which will take care of the download & cache for you , your main problem may be low network speed for many requests
Another thing to manage this network problem you may serial queue the download of the data that will help you load one part fastly and display it which will make the impression to the user that the app is in request for more data instead of make all the requests at once