ios - UILabel 未在 dispatch_group_notify 内部更新

Question

为什么这不起作用？

dispatch_group_notify(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0)) { () -> Void in
    println("Howdy, I get called")
    self.myLabel.text = "Hello Mr. Gordon Freeman"
}

消息已打印但未设置 UILabel 文本。

Answer 1

您只能更新主队列中的 UI 元素:

dispatch_group_notify(group, dispatch_get_main_queue()) {
    println("Howdy, I get called")
    self.myLabel.text = "Hello Mr. Gordon Freeman"
}