我的视图控制器（下面的代码）是从故事板segue（附加到UIButton）以模态方式呈现的。一旦（动态生成的）按钮被轻敲，它就会被解雇。由于某种原因，它不会随后被释放（保留计数为1）。
显然，第一个问题是两个对象（PPAPI和PPObjectCache）将此对象保存为委托（在viewDidLoad中注册），但是这两个对象都使用弱引用，如果我可以获得其他任何东西，它将自动被ARC清空保留它以释放它。我已经验证这些对象没有强烈引用此视图控制器。
我使用了Instruments（Allocations配置文件）来检查此对象的保留/释放，并且报告显示在代码下方。正如您所看到的，不平衡在UIKit或Foundation代码中，但我很难确切地知道在哪里或为什么。
有人能发现UIKit或者基金会持有我的视图控制器的原因吗？
#import "PPLoginViewController.h"
#import "PPAppDelegate.h"
@interface PPLoginViewController () {
NSArray *employeeIDs;
}
@end
@implementation PPLoginViewController
- (void)viewDidLoad {
[super viewDidLoad];
PPAPI *api = [PPAPI api];
[api subscribeToViewsOfType:@"employees" delegate:self];
[[PPObjectCache cache] subscribeToChangesToObjectsOfType:@"worker" delegate:self];
[api callMethod:@"main.tasks.get_employees" withParameters:@{} callback:nil];
}
// PPAPI view subscription delegate method
- (void)receivedObjectIDs:(NSArray *)objectIDs forViewType:(NSString *)viewType {
NSLog(@"%@: GOT VIEW", self);
dispatch_async(dispatch_get_main_queue(), ^{
employeeIDs = objectIDs;
[self reload];
});
}
// PPObjectCache delegate method
- (void)objectChanged:(id)object {
dispatch_async(dispatch_get_main_queue(), ^{
[self reload];
});
}
- (void)reload {
[[self.view.subviews filteredArrayUsingPredicate:[NSPredicate predicateWithBlock:^BOOL(id evaluatedObject, NSDictionary *bindings) {
return [evaluatedObject isKindOfClass:[UIButton class]];
}]] makeObjectsPerformSelector:@selector(removeFromSuperview)];
UIDevice *currentDevice = [UIDevice currentDevice];
CGFloat y = 75.f;
for (NSNumber *employeeID in employeeIDs) {
NSDictionary *employee = [[PPObjectCache cache] objectOfType:@"worker" withID:employeeID];
UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[button setTitle:employee[@"name"] forState:UIControlStateNormal];
button.titleLabel.font = [UIFont boldSystemFontOfSize:18.f];
button.tag = [employeeID integerValue];
button.frame = CGRectMake((self.view.bounds.size.width - 240.f) / 2.f, y, 240.f, currentDevice.userInterfaceIdiom == UIUserInterfaceIdiomPad ? 60.f : 45.f);
[button addTarget:self action:@selector(login:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:button];
y += currentDevice.userInterfaceIdiom == UIUserInterfaceIdiomPad ? 75.f : 65.f;
}
}
// UIButton action from above
- (void)login:(UIButton *)sender {
PPAppDelegate *delegate = (PPAppDelegate *)[UIApplication sharedApplication].delegate;
delegate.loggedInEmployee = [[PPObjectCache cache] objectOfType:@"worker" withID:@(sender.tag)];
// self.logoutButton is an @property (weak) set from the presenting view controller
self.logoutButton.title = [NSString stringWithFormat:@"Logout %@", delegate.loggedInEmployee[@"initials"]];
[self dismissViewControllerAnimated:YES completion:nil];
}
@end
分配报告如下（抱歉格式不佳）。如您所见，我的应用程序代码负责的事件都是平衡的（显示为保留/释放组或紧接着平衡调用）。 UIKit或Foundation的某些东西没有发布我的视图控制器！
# Event Type ∆ RefCt RefCt Timestamp Responsible Library Responsible Caller
0 Malloc +1 1 00:19.062.502 UIKit -[UIClassSwapper initWithCoder:]
1 Retain +1 2 00:19.062.991 UIKit -[UIRuntimeConnection initWithCoder:]
2 Retain +1 3 00:19.063.036 UIKit -[UIRuntimeConnection initWithCoder:]
3 Retain +1 4 00:19.063.230 UIKit UINibDecoderDecodeObjectForValue
4 Retain +1 5 00:19.063.274 UIKit UINibDecoderDecodeObjectForValue
5 Retain +1 6 00:19.063.315 Foundation -[NSObject(NSKeyValueCoding) setValue:forKey:]
6 Retain +1 7 00:19.063.388 UIKit -[UINib instantiateWithOwner:options:]
Release (2) -2 00:19.063.568 UIKit -[UINibDecoder finishDecoding]
8 Release -1 5 00:19.063.599 UIKit -[UINibDecoder finishDecoding]
10 Release -1 3 00:19.063.722 UIKit -[UIRuntimeConnection dealloc]
11 Release -1 2 00:19.063.755 UIKit -[UIRuntimeConnection dealloc]
12 Retain +1 3 00:19.063.920 UIKit -[UIStoryboardSegue initWithIdentifier:source:destination:]
Retain/Release (2) 00:19.067.387 Purchase -[PPMasterViewController prepareForSegue:sender:]
15 Retain +1 4 00:19.072.460 UIKit -[UIViewController setChildModalViewController:]
16 Retain +1 5 00:19.076.305 UIKit -[UINib instantiateWithOwner:options:]
17 Retain +1 6 00:19.076.366 UIKit -[UINib instantiateWithOwner:options:]
18 Retain +1 7 00:19.076.582 UIKit -[UIProxyObject initWithCoder:]
19 Retain +1 8 00:19.076.587 UIKit -[UIRuntimeConnection initWithCoder:]
20 Retain +1 9 00:19.080.167 UIKit UINibDecoderDecodeObjectForValue
21 Retain +1 10 00:19.080.230 UIKit UINibDecoderDecodeObjectForValue
22 Release -1 9 00:19.080.449 UIKit -[UINib instantiateWithOwner:options:]
23 Release -1 8 00:19.080.507 UIKit -[UINib instantiateWithOwner:options:]
24 Release -1 7 00:19.080.578 UIKit -[UINibDecoder finishDecoding]
Release (2) -2 00:19.080.602 UIKit -[UINibDecoder finishDecoding]
26 Release -1 5 00:19.080.716 UIKit -[UIRuntimeConnection dealloc]
Retain/Release (2) 00:19.081.788 Purchase -[PPAPI subscribeToViewsOfType:delegate:]
Retain/Release (2) 00:19.081.866 Purchase -[PPObjectCache subscribeToChangesToObjectsOfType:delegate:]
32 Retain +1 5 00:19.089.975 UIKit -[UIWindow _setRotatableClient:toOrientation:updateStatusBar:duration:force:isRotating:]
33 Retain +1 6 00:19.091.352 UIKit __91-[UIWindowController transition:fromViewController:toViewController:target:didEndSelector:]_block_invoke_0238
Retain/Release (2) 00:19.105.379 UIKit -[UIResponder becomeFirstResponder]
36 Retain +1 7 00:19.106.122 UIKit -[UIViewController presentViewController:withTransition:completion:]
37 Retain +1 8 00:19.106.142 UIKit -[UIViewController presentViewController:withTransition:completion:]
38 Release -1 7 00:19.108.717 UIKit _UIApplicationHandleEvent
39 Release -1 6 00:19.109.517 UIKit -[UIStoryboardSegue dealloc]
40 Release -1 5 00:19.109.534 UIKit _UIApplicationHandleEvent
41 Release -1 4 00:19.109.581 UIKit -[UIStoryboardScene dealloc]
Retain/Autorelease/Release (5) +1 00:19.145.293 Foundation -[NSConcreteHashTable countByEnumeratingWithState:objects:count:]
Retain (2) +2 00:19.151.847 Purchase -[PPLoginViewController receivedObjectIDs:forViewType:]
Retain (2) +2 00:19.151.874 Purchase __copy_helper_block_
Release (2) -2 00:19.151.888 Purchase -[PPLoginViewController receivedObjectIDs:forViewType:]
Release (2) -2 00:19.278.813 Purchase __destroy_helper_block_
48 Release -1 4 00:19.541.189 UIKit -[UIWindowController transitionViewDidComplete:fromView:toView:removeFromView:]
Retain/Release (2) 00:19.996.260 UIKit -[UIViewController _dismissViewControllerWithTransition:from:completion:]
51 Release -1 3 00:19.996.269 UIKit -[UIViewController _dismissViewControllerWithTransition:from:completion:]
52 Release -1 2 00:19.996.302 UIKit -[UIPeripheralHost(UIKitInternal) _stopPinningInputViewsOnBehalfOfResponder:]
53 Retain +1 3 00:19.996.776 UIKit -[UIViewController _dismissViewControllerWithTransition:from:completion:]
54 Retain +1 4 00:20.001.379 UIKit __91-[UIWindowController transition:fromViewController:toViewController:target:didEndSelector:]_block_invoke_0238
55 Release -1 3 00:20.002.196 UIKit -[UIViewController _dismissViewControllerWithTransition:from:completion:]
56 Retain +1 4 00:20.432.653 UIKit -[UIViewController _didFinishDismissTransition]
57 Release -1 3 00:20.432.658 UIKit -[UIViewController setChildModalViewController:]
58 Release -1 2 00:20.432.662 UIKit -[UIViewController _didFinishDismissTransition]
59 Release -1 1 00:20.432.706 UIKit -[UIWindowController transitionViewDidComplete:fromView:toView:removeFromView:]
Retain/Autorelease (2) +1 00:20.663.794 Foundation hashProbe
答案 0 :(得分：4)
这是我自己的愚蠢错误，正如我所料，但我会在这里回答，以防它对任何人都有用！
PPAPI维护一个NSHashTable，其中包含对视图订阅的弱引用，如果订阅的对象被释放，它将自动归零。看来，当从NSHashTable获取对象时，它们会被保留，然后由Foundation自动释放。
PPAPI正在后台GCD队列的while(1)循环内访问NSHashTable（这可能是糟糕的设计）。因为while(1)循环使队列保持忙碌，所以自动释放池从未耗尽，结果是PPLoginViewController被Foundation保留并且从未被释放。
解决方法是将while(1)循环的内容放在@autoreleasepool { }块中。
分配的线索是分配报告的最后一行，该报告显示Retain/Autorelease而不是Retain/Autorelease/Release。