Crash when creating UIImage from Data

Question

In my application, I'm attempting to instantiate a UIImage from Data. I've been seeing some crash logs come in from App Store Connect showing that my code is crashing on this particular line:

guard let data = photo.data, let image = UIImage(data: data) else { return nil }

Below is the backtrace. PhotoCache is the last object I have control over, and .imageFor(_:) is the method that the line above is contained in.

What is PFEvanscentData, and what might be causing it to crash in this scenario?

Edit: Here is the full method.

private var cache = NSCache()
    
func imageFor(_ photo: Photo) -> UIImage? {
    guard let key = photo.id as NSString? else { return nil }
    if let image = cache.object(forKey: key) {
        return image
    }
    guard let data = photo.data, let image = UIImage(data: data) else { return nil }
    cache.setObject(image, forKey: key)
    return image
}

user_12290741 · Answer

The problem might be in memory warnings. NSCache do not guarantee to remove cached images after receiving a memory warning. I would suggest to subclass NSCache and inside subclass listen (using NSNotificationCenter) for didReceiveMemoryWarningNotification and if you get an warning remove elements from cache.

user_6458001 · Answer

There are known thread safety issues with UIImage(data:) calls. A simple NSLock protection might help in this.

    lock.lock()
    let image = UIImage(data: data)
    lock.unlock()

References :

Alamofire https://github.com/Alamofire/AlamofireImage/blob/master/Source/UIImage%2BAlamofireImage.swift#L38-L53

AFNetworking https://github.com/AFNetworking/AFNetworking/blob/3e8addb6537df7ae535df402680a4be93ae7a6a6/AFNetworking/AFURLResponseSerialization.m#L522-L533

user_14355842 · Answer

It looks like it might be an issue of using an objective-c class within this swift class. I'm looking at the line

Data._unconditionallyBridgeFromObjectiveC

You probably need to double check that the NSData coming from Objective-C is actually non-nil and is being converted to the correct type that you are sending to the UIImage initializer, since there's nothing that's actively enforcing that on the Obj-C side you should make sure it is correct on the swift side.

Crash when creating UIImage from Data

3 Answers