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iOS Development: How can I induce low memory warnings on device?

Posted by: admin November 30, 2017 Leave a comment

Questions:

I’d like to test my app functions well in low memory conditions, but it’s difficult to test. How can I induce low memory warnings that trigger the didReceiveMemoryWarning method in my views when the app is running on the device, not the simulator? Or what are some ways I can test my app under these possible conditions?

The reason I can’t use the simulator is my app uses Game Center and invites don’t work on the simulator.

Answers:

To test on a device, just add some code that periodically allocates large chunks of memory without freeing it (i.e. leak on purpose). You can do this in a separate thread, or in response to a timer, or using whatever mechanism that best allows you to test and observe the behavior of your application.

You might also choose to create a separate app that does something similar and is designed to run in the background, if you’d like to easily reuse this and/or test with multiple applications.

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You can call the private method:

[[UIApplication sharedApplication] performSelector:@selector(_performMemoryWarning)];

Just remember to use it on debug only, or else your app will get rejected.

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The iOS Simulator’s Simulate Memory Warning menu item allows you to simulate a memory warning.

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Using Instruments, use the menu item: Instrument -> Simulate Memory Warning.

To use Instruments on your app from Xcode, use the Product -> Profile menu item.

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I’ve re-written Enzo Tran’s answer in Swift:

UIControl().sendAction(Selector(("_performMemoryWarning")), to: UIApplication.shared, for: nil)

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Theres a menu command that will invoke it.

Hardware > Simulate Memory Warning from the simulator.

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Converted @ChikabuZ to swift 3:

UIControl().sendAction(Selector(("_performMemoryWarning")), to: UIApplication.shared, for: nil)

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If someone, for whatever reason, tries to do this in Swift 3 – here is how to allocate 1.2 GB of ram.

   for i in 0...1200 {
      var p: [UnsafeMutableRawPointer] = []
      var allocatedMB = 0
      p.append(malloc(1048576))
      memset(p[allocatedMB], 0, 1048576);
      allocatedMB += 1;
   }