Reloading cells in view after image downloaded - swift

Question

I am currently learning swift. I have experience in android but now time for something new. I am starting with basics to load movie DB from API to table. I am storing dowloaded poster in Movie class (which also downloads them) when scrolling I can see the posters but after download the current cells in the view not updated, only after scroll. How can I implement callback from Movie to table view to update visible cells after download.
Movie:
import UIKit
let URL_PREFIX = "https://image.tmdb.org/t/p/original"
class Movie {
let movieId: CLong?
let title: String?
let posterPath: String?
let overview: String?
let releaseDate: String?
var posterImage: UIImage?
var callback: ((_ id: Int) -> Void)?
init(movieId: CLong,title: String,posterPath: String,overview: String,releaseDate: String,posterImage: UIImage?=nil) {
self.movieId = movieId
self.title = title
self.posterPath = posterPath
self.overview = overview
self.releaseDate = releaseDate
self.posterImage = posterImage
setResizedImage(path: posterPath)
}
func setResizedImage(path: String)
{
let conPath = URL_PREFIX + path
print("Path: \(conPath)")
guard let urlPath = URL(string: conPath) else {
print("You fucked up")
return
}
print("Download Started")
getData(from: urlPath) { data, response, error in
guard let _ = data, error == nil else { return }
print(response?.suggestedFilename ?? urlPath.lastPathComponent)
print("Download Finished")
//update
DispatchQueue.main.async()
{
self.posterImage = UIImage(data: data!)
}
}
}
}
MyViewController:
import UIKit
let URL_MOVIES = "https://api.themoviedb.org/3/movie/upcoming?
api_key=000";
class DataViewController: UIViewController,UITableViewDelegate,
UITableViewDataSource {
#IBOutlet weak var myTable: UITableView!
var movieArray :[Movie] = []
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return movieArray.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
guard let cell = tableView.dequeueReusableCell(withIdentifier: "MovieTableViewCell", for: indexPath) as? CustomTableViewCell else {
fatalError("The dequeued cell is not an instance of MovieTableViewCell.")
}
let movie = movieArray[indexPath.row]
cell.title.text = movie.title
cell.releaseDate.text = movie.releaseDate
cell.overview.text = movie.overview
//cell.url.text = movie.overview
if (movie.posterImage==nil)
{
print("Loaded placeholder")
cell.poster.image = UIImage(named: "poster")
}
else
{
print("Hello2")
cell.poster.image = movie.posterImage
}
return cell
}
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
print("You tapped cell number \(indexPath.row).")
}
override func viewDidLoad() {
super.viewDidLoad()
myTable.rowHeight = UITableView.automaticDimension
myTable.estimatedRowHeight = 50
getJsonFromUrl()
}
func getJsonFromUrl(){
let url = NSURL(string: URL_MOVIES)
URLSession.shared.dataTask(with: (url as URL?)!, completionHandler: {(data, response, error) -> Void in
if let jsonObj = try? JSONSerialization.jsonObject(with: data!, options: .allowFragments) as? NSDictionary {
if let resultArray = jsonObj.value(forKey: "results") as? NSArray
{
for film in resultArray
{
if let movieDict = film as? NSDictionary
{
//getting the name from the dictionary
let id = movieDict.value(forKey: "id")
let title = movieDict.value(forKey: "title")
let posterPath = movieDict.value(forKey: "poster_path")
let overview = movieDict.value(forKey: "overview")
let releaseDate = movieDict.value(forKey: "release_date")
let movie = Movie(movieId:id as! CLong, title: title as! String, posterPath: posterPath as! String, overview: overview as! String, releaseDate: releaseDate as! String)
self.movieArray.append(movie)
}
}
}
OperationQueue.main.addOperation({
self.myTable.reloadData()
})
}
}).resume()
}
}

Answer 1

You can add the download function inside the cell custom class and assign the imageView inside the callback, but this has many problems such as redownloading same image multiple times when scrolling, it's better to use SDWebImage or you can use Kingfisher Library
import SDWebImage
cell.poster.sd_setImage(with: URL(string:movie.imageUrlStr), placeholderImage: UIImage(named: "placeholder.png"))