Swift 完成处理程序在完成之前为True

所以我有一个函数，它从API中获取引用和作者。我有一个完成处理程序，这样我就可以获得quote和author，然后在Viewdidload函数中将它们设置为各自的UILabel。但由于某种原因，引用和作者都是零。处理程序出了什么问题

    func getJSON(completionHandler: @escaping(CompletionHandler)){
    if let quoteURL = URL(string: "http://quotes.rest/qod.json")

    {
        let session = URLSession.shared


        let task = session.dataTask(with: quoteURL)
        { (data, response, error) -> Void in
            if data != nil
            {
                let quoteData = JSON(data: data!)

                self.quote = quoteData["contents"]["quotes"][0]["quote"].stringValue
                self.author = quoteData["contents"]["quotes"][0]["author"].stringValue


            }
        }
        task.resume()
    }
     completionHandler(true)
}

在Viewdidload（）中调用函数

Swift不允许在后台进程中设置UILabel文本，这就是我无法在getJSON（）中设置UILabel文本的原因

---

谢谢

您需要将其插入回拨中

func getJSON(completionHandler: @escaping(CompletionHandler)){
    if let quoteURL = URL(string: "http://quotes.rest/qod.json") 
    {
        let session = URLSession.shared 
        let task = session.dataTask(with: quoteURL)
        { (data, response, error) -> Void in
            if data != nil
            {
                let quoteData = JSON(data: data!)

                self.quote = quoteData["contents"]["quotes"][0]["quote"].stringValue
                self.author = quoteData["contents"]["quotes"][0]["author"].stringValue 

                completionHandler(true) // set it inside the callback
            }
            else {
                completionHandler(false)
            }
        }
        task.resume()
    }
    else {
         completionHandler(false)
    }
}

func getJSON(completionHandler: @escaping(CompletionHandler)){
    if let quoteURL = URL(string: "http://quotes.rest/qod.json") 
    {
        let session = URLSession.shared 
        let task = session.dataTask(with: quoteURL)
        { (data, response, error) -> Void in
            if data != nil
            {
                let quoteData = JSON(data: data!)

                self.quote = quoteData["contents"]["quotes"][0]["quote"].stringValue
                self.author = quoteData["contents"]["quotes"][0]["author"].stringValue 

                completionHandler(true) // set it inside the callback
            }
            else {
                completionHandler(false)
            }
        }
        task.resume()
    }
    else {
         completionHandler(false)
    }
}