Discussion - Allocations and Leaks instruments
Extraordinarily hard to spot
Tough to find offending code without help from tools
Unbounded Memory Growth (memory growth without a chance to collect (deallocate) memory
True Leaks (retain cycles)
Allocations
Generation Analysis
Tracks allocations still resident when the generation is marked
- As you do multiple generations you will see only the new allocations since the last generations
Simulate Memory Warning (did it help, do you have anything observing for this?)
I have unbounded memory growth, now what?
- Look for the biggest offenders (sorting)
- Drill into the code and look for ways to release unnecessary allocations
Good ‘ol fashion memory management
If you’re intentionally holding onto objects, consider implementing an observer for UIApplicationDidReceiveMemoryWarningNotification to release them
Leaks / Retain Cycles aka. Strong Reference Cycles
Persistent vs. Transient
Static Code Analyis
Narrow list to your code
Use / Observe (detective work)
“You’re in the ballpark” now what?
Reference counting
Weak and Unowned
Closure example with capture list; weak and unowned
Apple says, “Use a weak reference whenever it is valid for that reference to become nil at some point during its lifetime. Use an unowned reference when you know that the reference will never be nil once it has been set during initialization.”
Picks
Darryl
Visual Debugging with Xcode WWDC 2016 Session 410 demonstrates the use of the new Memory Graph Debugger starting at about 24 minutes in
John
"Weak, Strong, Unowned, Oh My!" - a Guide to References in Swift by Hector Matos
