等待异步api调用完成 - Swift / IOS [英] Wait until an asynchronous api call is completed - Swift/IOS

问题描述

我正在一个ios应用程序，在我的appDelegate我有：

I'm working on an ios app where in my appDelegate I have:

func application(application: UIApplication!, didFinishLaunchingWithOptions launchOptions: NSDictionary!) -> Bool {


                self.api.signInWithToken(emailstring, token: authtokenstring) {
                    (object: AnyObject?, error:String?) in

                    if(object != nil){
                        self.user = object as? User
                        //go straight to the home view if auth succeeded
                        var rootViewController = self.window!.rootViewController as UINavigationController
                        let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
                        var homeViewController = mainStoryboard.instantiateViewControllerWithIdentifier("HomeViewController") as HomeViewControllerenter code here
                            rootViewController.pushViewController(homeViewController, animated: true)


                    }
                }

    return true

}

api.signInWithToken是一个使用Alamofire进行的异步调用，我想在func应用程序的末端返回true之前等待它完成。

The api.signInWithToken is an asynchronous call made with Alamofire, and I would like to wait for it's completion before returning true at the end end of func application.

推荐答案

注意：您应该不这样做，因为它阻止了线程。

Note: You should not do it this way, as it blocks the thread. See Nate's comment above for a better way.

有一种方法可以等待异步调用使用GCD完成。代码如下所示

There is a way to wait for an async call to complete using GCD. The code would look like the following

var semaphore = dispatch_semaphore_create(0)

performSomeAsyncTask {
    ...
    dispatch_semaphore_signal(semaphore)
}

dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER)
dispatch_release(semaphore)

维基百科有一个确定文章，以防您对信号量无所知晓。

Wikipedia has an OK article in case you know nothing about semaphores.

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