Swift - load PNG without caching

Question

I'm building a game that uses some images, and I load them in UIImageViews. By making some tests, I realized that the memory increases when I load the images, but do not decrease when I remove the UIImageView from superview.

Example:
- initial memory: 50mb
- then I load some images in many UIImageViews (that are inside a UIView)
- the memory goes to about 70mb
- remove all UIImageViews from superview, and then remove the UIView
- the memory keeps 70mb

It seems like the loaded PNG (in this case, I use assets to storage all of them) keeps in memory/cached, and only "decache" when the app closes.

How can I resolve this? When the app goes to about 70-80mb, the app starts to become slower, and it is very frustrating.

It would help if you post some code. Are you downsizing your PNG's to an appropriate size for the device? (i.e. no point putting a 4000x4000 image in the asset catalog, if you are only going to display it with 200x200 dimensions. You might also want to look at autoreleasepool. https://stackoverflow.com/questions/25860942/is-it-necessary-to-use-autoreleasepool-in-a-swift-program — rbaldwin, May 06 '18 at 07:24
The code I use is basically load the UIImageView with UIImage(named: filename). I'm testing now contentsOfFile. The files have only the needed size for the device. — LeMag, May 06 '18 at 07:45

score 0 · Answer 1 · answered May 06 '18 at 10:39

You can use this code it will not store the image in cache

extension UIImageView {
    func downloadedFrom(url: URL, contentMode mode: UIViewContentMode = .scaleToFill) {
        contentMode = mode
        URLSession.shared.dataTask(with: url) { data, response, error in
            guard
                let httpURLResponse = response as? HTTPURLResponse, httpURLResponse.statusCode == 200,
                let mimeType = response?.mimeType, mimeType.hasPrefix("image"),
                let data = data, error == nil,
                let image = UIImage(data: data)
                else { return }
            DispatchQueue.main.async() {
                self.image = image
            }
            }.resume()
    }
    func downloadedFrom(link: String, contentMode mode: UIViewContentMode = .scaleToFill ) {
        guard let url = URL(string: link) else { return }
        downloadedFrom(url: url, contentMode: mode)
    }
    func downloadimageFrom(url: URL, contentMode mode: UIViewContentMode = .scaleToFill) {
        contentMode = mode
        URLSession.shared.dataTask(with: url) { data, response, error in
            guard
                let httpURLResponse = response as? HTTPURLResponse, httpURLResponse.statusCode == 200,
                let mimeType = response?.mimeType, mimeType.hasPrefix("image"),
                let data = data, error == nil,
                let image = UIImage(data: data)
                else { return }
            DispatchQueue.main.async() {

                self.image = image

            }
            }.resume()
    }
    func downloadimageFrom(link: String, contentMode mode: UIViewContentMode = .scaleToFill ) {
        guard let url = URL(string: link) else { return }
        downloadimageFrom(url: url, contentMode: mode)
    }


}

Swift - load PNG without caching

1 Answers1