我是IOS应用程序开发的新手。我试图阻止viewWillAppear在我的函数完成工作之前完成。我该怎么做？这里是viewWillAppear:overridefuncviewWillAppear(animated:Bool){super.viewWillAppear(true)checkFacts()ifreset!=0{print("removingallbirdfacts")birdFacts.removeAll()}}funccheckFacts(){letdate=getDate()varx:Bool=truevarind:Int=0print("countis",birdF