How to release the private property in iOS 7 using ARC

Question

I am developing a project on iOS 7 using ARC, I want to release a private property when the viewController is released
Here is the TestViewController that is presented as a modal view controller, setting a value to the private property testAVPlayer in viewDidLoad:

//TestViewController.m
#import "TestAVPlayer.h"
@interface TestViewController () {
    TestAVPlayer *testAVPlayer;
}

@end

- (void)viewDidLoad
{
    [self setupPlayer];
}

- (void)setupPlayer {
    AVPlayerItem *item = [AVPlayerItem playerItemWithURL:[[NSBundle mainBundle] URLForResource:@"music" withExtension:@"mp3"]];
    testAVPlayer = [TestAVPlayer playerWithPlayerItem:item];

    [testAVPlayer setActionAtItemEnd:AVPlayerActionAtItemEndNone];
    [testAVPlayer play];
}

- (void)dealloc {
    NSLog(@"dealloc TestViewController: %@", self);
}

TestAVPlayer is a subclass of AVPlayer, I put a NSLog into the dealloc

// TestAVPlayer.h
#import <AVFoundation/AVFoundation.h>

@interface TestAVPlayer : AVPlayer

@end

//  TestAVPlayer.m
#import "TestAVPlayer.h"

@implementation TestAVPlayer

- (void)dealloc {
    NSLog(@"dealloc testAVPlayer: %@", self);
}
@end

When TestViewController is dismissed, the testAVPlayer seems never be released, I see the "dealloc TestViewController", but there is no "dealloc testAVPlayer" in console log

Answer 1

I tried your code, the problem is that even if you call [TestAVPlayer playerWithPlayerItem:item] the TestAVPlayer class doesn't have such method, so it will call playerWithPlayerItem: function from the AVPlayer base class, which will return an instance of the AVPlayer class instead of the TestAVPlayer class. The compiler won't give you any warning because the playerWithPlayerItem: method returns a type of id. If you check this with the debugger you'll see that the private variable's type is not TestAVPlayer:

The dealloc of the TestAVPlayer will never be called as no such object was created. The AVPlayer instance gets deallocated when the TestViewController is deallocated. You can check this by using Instruments or simply adding a Symbolic Breakpoint to [AVPlayer dealloc].

Select the Breakpoint Navigator and click on the + button and add a Symbolic Breakpoint.

Write [AVPLayer dealloc] to the Symbol field and press Enter. When you run the application and the TestViewController gets deallocated then you will see that the breakpoint will be hit, hence the AVPlayer really gets deallocated.

Answer 2

You are using a class factory method to initialize your object, which means that you do not own the testAVPlayer object and thus are not responsible for releasing it.

See Class Factory Methods from the Concepts in Objective-C Programming guide for more details.

If you indeed want to own and control the lifetime of this object, use the following initializer:

testAVPlayer = [[TestAVPlayer alloc] initWithPlayerItem:item];

and your dealloc method will be called.

Answer 3

testAVPlayer = [AVPlayer playerWithPlayerItem:playerItem];

You are using AVPlayer, not your TestAVPlayer.

Answer 4

Try implementing - viewDidUnload then nil the testAVPlayer:

- (void) viewDidUnload
{
    [super viewDidUnload];
    testAVPlayer = nil;
} 

Answer 5

Although you are calling it as [TestAVPlayer playerWithPlayerItem:item], you are really getting back an instance of AVPlayer, not TestAVPlayer. In fact, the AVPlayer instance you created really IS getting deallocated. You won't be able to see your log in dealloc because an instance of that class is never created.

As suggested by another, replace [TestAVPlayer playerWithPlayerItem:item] with [[TestAVPlayer alloc] initWithPlayerItem:item]; and you should start seeing your logs.