等到异步api调用完成 – Swift / IOS

发布时间：2020-12-14 04:57:14 所属栏目：百科来源：网络整理

导读：我正在开发一个ios应用程序,我的appDelegate中有： func application(application: UIApplication!,didFinishLaunchingWithOptions launchOptions: NSDictionary!) - Bool { self.api.signInWithToken(emailstring,token: authtokenstring) { (object: AnyOb

我正在开发一个ios应用程序,我的appDelegate中有：

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是一个用Alamofire进行的异步调用,我想在func应用程序的最后一端返回true之前等待它的完成.

解决方法

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

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OK article,如果您对信号量一无所知.

（编辑：李大同）

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