Swift UIImage Array from JSON URL

Question

I try to create an Array of UIImages from a URL Array received from a JSON Request to show them afterwards in a UITableView. But somehow my UIImage Array stays Empty and is not receiving any Data. The other Arrays for example memeURL are receiving all Data correct but memePics.count stays on 0.

Would be great if someone could show me what i am doing wrong. Also if for this task there is a better way on how to do it - it would be also appreciated!

Var:

var memePics: [UIImage] = []

Loop to add Images to Array:

while(i < memeURL.count) {
            MemeAPI.requestAPIImageFile(url: memeURL[i]) { (image, error) in
                guard let image = image else {
                    print("PIC IS NIL")
                    return
                }
                self.memePics.append(image)
                i+=1
            }
        }

RequestAPIImageFile Function:

class func requestAPIImageFile(url: URL, completionHandler: @escaping (UIImage?, Error?) -> Void) {
        let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
            guard let data = data else {
                completionHandler(nil, error)
                return}
            let downloadedImage = UIImage(data: data)
            completionHandler(downloadedImage, nil)
        }
        task.resume()
    }

Not related: while(i < memeURL.count) { doSomethingAsync {i+1} } => DispatchGroup, enter, leave, notify. — Larme
– Larme, Commented May 11, 2020 at 16:08
@JoakimDanielson: No its the same API just 2 different Functions - first (not showed in my example) for receiving Data like URL of the IMG, Name etc - this one is working fine. And the other Function for Downloading the Image from URL. koen: No - the Console does not Print out an Error or my Custom Print which means the guard seems to pass fine. — Midoxx
– Midoxx, Commented May 11, 2020 at 16:13
I still don't understand, in the first closure for the MemeAPI call you are adding the result to an UIImage array and in the second closure for URLSession you are creating an UIImage instance so to me it looks like you are getting your images from 2 different sources. — Joakim Danielson
– Joakim Danielson, Commented May 11, 2020 at 16:19

Shehata Gamal · Accepted Answer · 2020-05-11 16:11:25Z

1

Add plus line out of callback

  self.memePics.append(image)
  }
  i+=1

and use DispatchGroup to be notified on finish like

let g = DispatchGroup()
memeURL.forEach {  
        g.enter()
        MemeAPI.requestAPIImageFile(url:$0) { (image, error) in
            guard let image = image else {
                print("PIC IS NIL")
                return
            }
            self.memePics.append(image) 
            g.leave()
        }
} 
g.notify(queue:.main) {
   print("All done")
}

answered May 11, 2020 at 16:11

Shehata Gamal

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1 Comment

Midoxx Over a year ago

Thanks so much it is working now! I´ve now put both of my Functions in the Dispatch Group and the arrays works fine. Still have 1 Problem but I will create another Post for this - Thanks again!

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