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考慮下面的代碼兩次:崩潰調用dispatch_source_create()時連續
@interface ViewController()
@property (nonatomic, strong) dispatch_source_t source;
@end
@implementation ViewController
-(void)viewDidLoad {
[super viewDidLoad];
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
self.source = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
self.source = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
dispatch_resume(self.source);
dispatch_source_set_timer(self.source, dispatch_time(DISPATCH_TIME_NOW, 0.2 * NSEC_PER_SEC), 0.2 * NSEC_PER_SEC, 0.1 * NSEC_PER_SEC);
dispatch_source_set_event_handler(self.source, ^{
NSLog(@"%s",__func__);
});
}
@end
如果我使用dispatch_source_create
創建同樣DISPATCH_SOURCE_TYPE_TIMER
兩次,應用程序會崩潰。爲什麼?
在上面的例子中創建一次和兩次調度源之間是否有區別?
libdispatch.dylib`_dispatch_xref_dispose:
0x10015e174 <+0>: ldr w8, [x0, #48]
0x10015e178 <+4>: cmp w8, #2 ; =2
0x10015e17c <+8>: b.hs 0x10015e184 ; <+16>
0x10015e180 <+12>: ret
0x10015e184 <+16>: stp x20, x21, [sp, #-16]!
0x10015e188 <+20>: adrp x20, 41
0x10015e18c <+24>: add x20, x20, #3849 ; =3849
0x10015e190 <+28>: adrp x21, 46
0x10015e194 <+32>: add x21, x21, #2440 ; =2440
0x10015e198 <+36>: str x20, [x21]
0x10015e19c <+40>: ldp x20, x21, [sp], #16
-> 0x10015e1a0 <+44>: brk #0x1
爲什麼要那樣做?當你將第二個賦值給同一個屬性時,第一個將被釋放, – Paulw11
@ Paulw11我知道這是無意義的代碼,第一個將在分配第二個時釋放,但是然後我繼續第二個。方式會崩潰,我認爲它仍然會正常工作,但它確實如此! – Jimmy
由於處理調度對象時發生崩潰,它看起來像是一個計時問題。 – Paulw11