iOS - Out of Memory

Some time ago, I started seeing an explosion of “Out of memory” crashes in Dash. Bugsnag wouldn’t tell me much more than this:

This started to happen with iOS version 14.4.2, and subsequent OS versions. Without much to go around with, I decided to fix a warning I had lingering:

Well, you can guess where this is heading. At some point, around 14.4.2, the OS started to kill my app. I was using unavailable methods inside extensions. The culprit was the usage of UIApplicationMain inside an extension.

So I wrote this abstraction:

 public protocol MainApplication {
  
  func registerForRemoteNotifications()
  func unregisterForRemoteNotifications()
  var isRegisteredForRemoteNotifications: Bool { get }
  
  var alternateIconName: String? { get }
  func setAlternateIconName(
    _ alternateIconName: String?,
    completionHandler: ((Error?) -> Void)?
  )
  
  
  func canOpenURL(_ url: URL) -> Bool
}

In the main app:

extension UIApplication: MainApplication {}

And on the extension:

struct DummyMainApplication: MainApplication {
  init() {}
  
  func registerForRemoteNotifications() {}
  func unregisterForRemoteNotifications() {}
  var isRegisteredForRemoteNotifications: Bool { return true }
  
  var alternateIconName: String? { return nil }
  func setAlternateIconName(
    _ alternateIconName: String?,
    completionHandler: ((Error?) -> Void)?
  ) {}
  
  
  func canOpenURL(_ url: URL) -> Bool { return true }
}

Finally, turning Require Only App-Extension-Safe API to True, allowed me to quickly audit the codebase.

After releasing Dash 1.6 with these fixes, I haven’t see any crash due to Out of Memory.