小编Tao*_*Tao的帖子

我在viewcontroller中有一个UIWebView,它有两个方法如下.问题是如果我在第二个线程完成之前弹出(点击导航栏)此控制器,应用程序将在[super dealloc]之后崩溃,因为"试图从主线程以外的线程获取Web锁定或这可能是从辅助线程调用UIKit的结果." 任何帮助将非常感激.

-(void)viewDidAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    NSInvocationOperation *operation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(load) object:nil];
    [operationQueue addOperation:operation];
    [operation release];
}

-(void)load {
    [NSThread sleepForTimeInterval:5];
    [self performSelectorOnMainThread:@selector(done) withObject:nil waitUntilDone:NO];
}

如果a与c相同,b与c相同,为什么a与b不相同？

var a = [1, 2, 3]
var b = a
var c = a[0...2]
a === c                    // true
b === c                    // true
a === b                    // false

如果a,b,c是常数:

let a = [1, 2, 3]
let b = a
let c = a[0...2]
a === c                    // true
b === c                    // true
a === b                    // true