ios - 关于 KVO 在 iOS 10 和 iOS 11 中不带 `removeObserver:forKeyPath:` 的不同行为

Question

有一次我在使用 KVO 时忘记调用“removeObserver:forKeyPath:”。在iOS10模拟器上，模拟器崩溃了。但在iOS11模拟器上一切正常。没有内存泄漏，也没有崩溃。

我很困惑为什么不调用“removeObserver:forKeyPath:”会导致不同 SDK 版本上的不同结果。

这里是演示代码:

#import <UIKit/UIKit.h>
@interface GSObject : NSObject

@end
@interface GSObject ()

@property (nonatomic, assign) NSInteger integer;

@end

@implementation GSObject

- (instancetype)init {
    if (self = [super init]) {
        [self addObserver:self forKeyPath:@"integer" options:NSKeyValueObservingOptionInitial context:nil];
    }
    return self;
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object 
change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void 
*)context {
    NSLog(@"%@",object);
}
@end

int main(int argc, char * argv[]) {
    @autoreleasepool {
        GSObject *object = [[GSObject alloc] init];
        object = nil;
    }
}

Answer 1

I'm confused why I didn't call "removeObserver:forKeyPath:" it shows different result on different sdk version.

那是因为不同的SDK版本不同。他们的行为不同。这就是“不同”的含义。。

请阅读发行说明，https://developer.apple.com/library/archive/releasenotes/Foundation/RN-Foundation/index.html :

Prior to 10.13 [and iOS 11], KVO would throw an exception if any observers were still registered after an autonotifying object's -dealloc finished running.