why downloading image from url returns nil? [duplicate]

This question already has an answer here:

I am trying to download an image that is uploaded to my database storage and the link to the image is in my Real time database. There is no problem with the link but when I use my method to return the image from the link I am getting nil. I force wrap it because it needs to return an image for now.

This is my code:

func getImageFromUrl(url: URL) -> UIImage
var tempImage: UIImage? = nil

print("INSIDE URL -> (url.absoluteString)")

URLSession.shared.dataTask(with: url) (data, response, error) in
if error != nil
print("Error on getImageFromUrl : (error!.localizedDescription)")
return


print("Image data " + data.debugDescription)

DispatchQueue.main.async
tempImage = UIImage(data: data!)!
print("TEMP IMAGE > (String(describing: tempImage?.images![0]))")

.resume()

if tempImage == nil
print("IMAGE IS NIL!")

return tempImage!



Please let me know why my code is failing.

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

1 Answer
1

The problem with your code is that the dataTask method is asynchronous. You are returning the result before the download process is completed. What you need is to add a completion handler to your method to return the image or the error once finished:

import UIKit
import PlaygroundSupport

PlaygroundPage.current.needsIndefiniteExecution = true

func getImage(from url: URL, completion: @escaping (UIImage?, Error?) -> ())
print("download started:", url.absoluteString)
URLSession.shared.dataTask(with: url) data, reponse, error in
guard let data = data else
completion(nil, error)
return

print("download finished:")
completion(UIImage(data: data), nil)
.resume()



let url = URL(string: "https://i.stack.imgur.com/varL9.jpg")!
getImage(from: url) image, error in
guard let image = image else
print("error:", error ?? "")
return

print("image size:", image.size)
// use your image here and don't forget to always update the UI from the main thread
DispatchQueue.main.async
self.imageView.image = image




"image size: (3072.0, 2304.0)n"