从一个crash体验strong的延迟释放

@interface ViewController ()
@property (nonatomic, strong) Manager *strongManager;
@property (nonatomic, strong) Operation *strongOperation;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    UIButton *btn = [[UIButton alloc] initWithFrame:CGRectMake(100, 100, 100, 100)];
    [btn setBackgroundColor:[UIColor redColor]];
    [btn addTarget:self action:@selector(btnAction:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:btn];
    // 模拟网络请求
    self.strongManager = [Manager new];
    __weak typeof(self) weakSelf = self;
    self.strongManager.endBlock = ^{
        weakSelf.strongManager = nil;
    };
    
    self.strongOperation = [Operation new];
    [self.strongOperation setTarget:self.strongManager selector:@selector(testMethod)];
}

- (void)btnAction:(id)sender{
    [self.strongOperation performCallBack]; // <- 1
}

@interface Manager : NSObject
@property (nonatomic, copy) void(^endBlock)(void);

- (void)testMethod;
@end

@implementation Manager
- (void)testMethod{
    if (self.endBlock) {
        self.endBlock();
    }
    NSLog(@"%@", self);
}

- (void)dealloc{
    NSLog(@"dealloc");
}
@end

@interface Operation : NSObject
@property (nonatomic, weak) id target;
@property (nonatomic, assign)SEL finishSelector;
- (void)setTarget:(id)target selector:(SEL)selector;

- (void)performCallBack;
@end

@implementation Operation
- (void)setTarget:(id)target selector:(SEL)selector{
    self.target = target;
    self.finishSelector = selector;
}

- (void)performCallBack{
    NSMethodSignature *signature = [self.target methodSignatureForSelector:self.finishSelector];
    NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:signature];
    [invocation setTarget:self.target];
    [invocation setSelector:self.finishSelector];
    [invocation invoke];
}
@end

@interface ViewController ()

@property (nonatomic, strong) Manager *manager;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    //正常写代码的时候还是推荐使用self.debugObj这种形式, 这里是为了排除干扰因素于是全部是用ivar的方式
    _manager = [Manager new];
    __weak typeof(self) weakSelf = self;
    _manager.testBlock = ^{
        weakSelf.manager = nil;
    };
    //发起网络请求
    [self.manager networkRequest]; //<- 2
}

@end

Manager
.h略过

@implementation Manager

- (void)dealloc {
    NSLog(@"dealloc");
}

- (void)networkRequest {
    Operation *operation = [Operation new];
    operation.target = self;
    operation.selector = @selector(networkCallBack);
    [operation performCallback];
}
// call back
- (void)networkCallBack {
    if (self.testBlock) {
        self.testBlock();
    }
    NSLog(@"%@", self);
}

@end

Operation .h .m
和文章开头demo中的operation一样

// Prepare a value at +0 for return through a +0 autoreleasing convention.
id 
objc_retainAutoreleaseReturnValue(id obj)
{
    if (prepareOptimizedReturn(ReturnAtPlus0)) return obj;

    // not objc_autoreleaseReturnValue(objc_retain(obj)) 
    // because we don't need another optimization attempt
    return objc_retainAutoreleaseAndReturn(obj);
}

// Accept a value returned through a +0 autoreleasing convention for use at +1.
id
objc_retainAutoreleasedReturnValue(id obj)
{
    if (acceptOptimizedReturn() == ReturnAtPlus1) return obj;

    return objc_retain(obj);
}

[self.manager networkRequest];

id temp = [self manager];
[temp networkRequest];