ios - NSUndoManager removeAllActionsWithTarget崩溃

我有一些简短的iOS Objective-C示例代码(从较大的项目简化)，导致我无法解释的NSUndoManager崩溃。

也就是说，当仅由NSUndoManager保留的对象进行释放时(因为它超出了undo级别)，并且根据docs调用removeAllActionsWithTarget:self的要求，我得到了EXC_BAD_ACCESS。

// SimpleViewController.m
@interface ViewController ()
@property (nonatomic, strong) NSUndoManager *undoManager;
@end

@implementation ViewController

@synthesize undoManager;

// called from a simple button
- (IBAction)doItTapped:(id)sender
{
    CoolObject *object = [CoolObject new];
    object.undoManager = self.undoManager;
    // according to docs, object will be retained by NSUndoManager here
    // but target will not (which should be okay)
    [self.undoManager registerUndoWithTarget:self selector:@selector(notCool:) object:object];
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.undoManager = [NSUndoManager new];
    self.undoManager.levelsOfUndo = 3;
}

和

// CoolObject.m
@implementation CoolObject

- (void)dealloc
{
    [self.undoManager removeAllActionsWithTarget:self];
}

@end

第四次点击按钮(levelsOfUndo + 1)后，它崩溃。
如果我将NSUndoManager与GCUndoManager交换，则不会崩溃。
在iOS 10.2 SIM和设备中测试。

感谢您的任何想法!

最佳答案

由于您在使用self.undoManager的那一刻未保留ojit_code，因此他们很可能会收到此错误。当对象已经被释放并尝试访问它时，您将获得错误的访问异常。

尝试从此更改代码:

CoolObject *object = [CoolObject new];

对此:

@interface ViewController (){
CoolObject *object;
}
@property (nonatomic, strong) NSUndoManager *undoManager;
@end
@implementation ViewController
- (IBAction)doItTapped:(id)sender
{
    object = [CoolObject new];
    object.undoManager = self.undoManager;
    // according to docs, object will be retained by NSUndoManager here
    // but target will not (which should be okay)
    [self.undoManager registerUndoWithTarget:self selector:@selector(notCool:) object:object];
}
@end

希望这会有所帮助。

关于ios - NSUndoManager removeAllActionsWithTarget崩溃，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/41602669/