如何重构代码以在主线程上调用AppDelegate? [英] How do I refactor my code to call AppDelegate on the main thread?

问题描述

我最近开始将项目从Swift3/Xcode8迁移到Swift4/Xcode9.我的应用程序在运行时崩溃，因为主线程清理程序仅允许在主线程上访问UIApplication.shared.delegate，从而导致启动时崩溃.我有以下代码，在Swift 3中效果很好-

I recently started migrating my project from Swift3/Xcode8 to Swift4/Xcode9. My app crashes at runtime because the main thread sanitizer allows access to UIApplication.shared.delegate only on the main thread, resulting in a crash at startup. I have the following code, which worked fine in Swift 3 -

static var appDelegate: AppDelegate {
    return UIApplication.shared.delegate as! AppDelegate;
}

我代码中的其他类可以访问appDelegate.我需要找出一种从主线程返回UIApplication.shared.delegate的方法.

Other classes in my code make access to appDelegate. I need to figure out a way to return UIApplication.shared.delegate from the main thread.

注意:从任何地方访问appDelegate的地方都不能使用DispatchQueue.main.async{}块.只需要在static var appDelegate声明中使用它.

Note: Using an DispatchQueue.main.async{} block from wherever access is made to appDelegate is not an option. Need to use it only within the static var appDelegate declaration only.

寻找一个聪明的解决方法.

Looking for a clever workaround.

相关的崩溃消息:

主线程检查器:在后台线程上调用的UI API:-[UIApplication委托] PID:1094，TID:30824，线程名称:(none)，队列名称:NSOperationQueue 0x60400043c540(QOS:469)，QoS:0

Main Thread Checker: UI API called on a background thread: -[UIApplication delegate] PID: 1094, TID: 30824, Thread name: (none), Queue name: NSOperationQueue 0x60400043c540 (QOS: UNSPECIFIED), QoS: 0

推荐答案

使用调度组解决.

static var realDelegate: AppDelegate?;

static var appDelegate: AppDelegate {
    if Thread.isMainThread{
        return UIApplication.shared.delegate as! AppDelegate;
    }
    let dg = DispatchGroup();
    dg.enter()
    DispatchQueue.main.async{
        realDelegate = UIApplication.shared.delegate as? AppDelegate;
        dg.leave();
    }
    dg.wait();
    return realDelegate!;
}

并在其他地方调用它

let appDelegate = AppDelegate(). realDelegate!

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