FS.O6 FS.O6 - 1 month ago 60
iOS Question

Run a background thread on Swift 3

I have a function that goes like this:

fileprivate func setupImageViewWithURL(url: URL) {
var image: UIImage? = nil
do {
try image = UIImage(data: Data(contentsOf: url))!
} catch is NSError {
print("Failed")
}

image = self.imageWithImage(sourceImage: image!, scaledToWidth: UIScreen.main.bounds.size.width)
self.imageImageView.image = image
self.imageImageView.frame = CGRect(x: 0, y: 0, width: UIScreen.main.bounds.size.width, height: (image?.size.height)!)
}


I want to run it on a
Background
thread
.

I've tried the
GDC
methods of
Swift2
but it didn't worked.

Did anything changed on the thread topic in
Swift3
?

Thank you!

Answer

It's OK to load image on the background, but it's not OK to perform UI updates on background thread. That's why the function must contain two threads.

func setupImageViewWithURL(url: URL) {
    var image: UIImage? = nil

    DispatchQueue.global().async { 
        do {
            try image = UIImage(data: Data(contentsOf: url))!
        } catch {
            print("Failed")
        }
        DispatchQueue.main.async(execute: {
            if image != nil {
                image = self.imageWithImage(sourceImage: image!, scaledToWidth: UIScreen.main.bounds.size.width)
                self.imageImageView.image = image
                self.imageImageView.frame = CGRect(x: 0, y: 0, width: UIScreen.main.bounds.size.width, height: (image?.size.height)!)
            }
        })
    }
}
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