How to detect memory warnings in iOS App Extension - ios

Question

I'm writing an iOS extension that extends NEPacketTunnelProvider in the NetworkExtension framework released in iOS 9. I'm running into a situation where iOS is killing the extension once hits 6MB of memory used.
In a regular iOS app, there are two ways to detect memory warnings and do something about it. Either via [UIApplicationDelegate applicationDidReceiveMemoryWarning:(UIApplication*)app] or [UIViewController didReceiveMemoryWarning]
Is there a similar way to detect memory warnings within an extension? I've searched up and down the iOS extension documentation but have come up empty thus far.

Answer 1

ozgur's answer does not work. UIApplicationDidReceiveMemeoryWarningNotification is a UIKit event and I haven't found a way to get access to that from an extension. The way to go is the last of these options: DISPATCH_SOURCE_TYPE_MEMORYPRESSURE.
I've used the following code (Swift) in a Broadcast Upload Extension and have confirmed with breakpoints that it is called during a memory event right before the extension conks out.
let source = DispatchSource.makeMemoryPressureSource(eventMask: .all, queue: nil)
let q = DispatchQueue.init(label: "test")
q.async {
source.setEventHandler {
let event:DispatchSource.MemoryPressureEvent = source.mask
print(event)
switch event {
case DispatchSource.MemoryPressureEvent.normal:
print("normal")
case DispatchSource.MemoryPressureEvent.warning:
print("warning")
case DispatchSource.MemoryPressureEvent.critical:
print("critical")
default:
break
}
}
source.resume()
}

Answer 2

I am not very familiar with the extensions API, however my basic hunch says that you can register any of your object as observers of UIApplicationDidReceiveMemoryWarningNotification from within that class:
NSNotificationCenter.defaultCenter().addObserverForName(UIApplicationDidReceiveMemoryWarningNotification,
object: nil, queue: .mainQueue()) { notification in
print("Memory warning received")
}