Question

I’m trying to memory test my app.

I’ve followed the Organizer – Documentation article entitled “Recovering Memory You Have Abandoned”, but I’m not sure if the results make my tested page good or bad, or somewhere in-between.

(My test involved: navigate to page 2, going back to page 1, press ‘Mark Heap’ -repeated 25 times for good measure.)

Attached is a screenshot of my allocations test. Most of the #Persistent values are 0. But there are some anomalies. Are these typical?

(The last Heapshot, 26, was taken after stopping the recording, and pressing ‘Mark Heap’ at the end of the trace – as suggested in the documentation.)

I would be very grateful for some advice. Thanks.

Answer 1

I believe that you are using ARC, and if you are using ARC, there is no need of bothering about the heaps, it will take care of everything.

Here are the 9 simple points from Apple’s docs to be in mind while using ARC:

ARC imposes some new rules that are not present when using other
compiler modes. The rules are intended to provide a fully reliable
memory management model; in some cases, they simply enforce best
practice, in some others they simplify your code or are obvious
corollaries of your not having to deal with memory management. If you
violate these rules, you get an immediate compile-time error, not a
subtle bug that may become apparent at runtime.

1. You cannot explicitly invoke dealloc, or implement or invoke retain,
   release, retainCount, or autorelease.
   The prohibition extends to using @selector(retain), @selector(release), and so on.

2. You may implement a dealloc method if you need to manage resources other than releasing instance variables. You do not have to
   (indeed you cannot) release instance variables, but you may need to
   invoke [systemClassInstance setDelegate:nil] on system classes and
   other code that isn’t compiled using ARC.
   Custom dealloc methods in ARC do not require a call to [super dealloc] (it actually results in a compiler error). The
   chaining to
   super is automated and enforced by the compiler.

3. You can still use CFRetain, CFRelease, and other related functions
   with Core Foundation-style

4. You cannot use NSAllocateObject or NSDeallocateObject.

5. You create objects using alloc; the runtime takes care of
   deallocating objects.

6. You cannot use object pointers in C structures.
   Rather than using a struct, you can create an Objective-C class to manage the data instead.
   There is no casual casting between id and void *.

7. You must use special casts that tell the compiler about object lifetime. You need to do this to cast between Objective-C objects and
   Core Foundation types that you pass as function arguments. For more
   details, see “Managing Toll-Free Bridging.”

8. You cannot use NSAutoreleasePool objects.
   ARC provides @autoreleasepool blocks instead. These have an advantage of being more efficient than NSAutoreleasePool.

9. You cannot use memory zones.
   There is no need to use NSZone any more—they are ignored by the modern Objective-C runtime anyway.