ios - swift 如何等到值改变

Question

我正在编写一个应用程序来测试您的古典希腊语能力。我有几个 View Controller 。在测试 View Controller 中，我有一个巨大的“开始”按钮，按下它会启动一系列代码，如下所示:

@IBAction func test(_ sender: Any) {
        beginBtn.isHidden = true
        beginBtn.isEnabled = false
        answerOne.isHidden = false
        answerTwo.isHidden = false
        answerThree.isHidden = false
        answerFour.isHidden = false
        data.currentNumOQue = (data.qCQ + data.qWQ + data.qSQ)
    if data.chooseCAlertDataLoaded == false {
        data.chooseCharacterQuestionType.addAction(data.chooseCharacterQuestionTypeEngGrk)
        data.chooseCharacterQuestionType.addAction(data.chooseCharacterQuestionTypeGrkEng)
        data.chooseCAlertDataLoaded = true
    } else {
        print("not first question")
    }
    while data.currentQC <= data.qCQ {
        present(data.chooseCharacterQuestionType, animated: false, completion: nil)
        DispatchQueue.global(qos: .background).async {
            while data.chooseCAlertReturnsEngGrk == nil {

            }
            DispatchQueue.main.sync {
                if data.chooseCAlertReturnsEngGrk == true {
                    //Eng-Grk QUestion
                    data.chooseCAlertReturnsEngGrk = nil
                } else {
                    //Grk=Eng QUestion
                    data.chooseCAlertReturnsEngGrk = nil
                }
            }
        }
        data.currentQC += 1
        data.currentQ += 1
    }
    data.currentQC = 1
    data.currentQW = 1
    data.currentQS = 1

}

任何人都可以帮助我如何等到值 chooseCAlertReturnsEngGrk 不为 nil 并继续执行，但这样做时不会“卡住”UI？

Answer 1

覆盖 didSet 来调用一些函数..然后在那个回调函数中，用参数做任何你想做的事..

class DataSomething {
    var chooseCAlertReturnsEngGrkObserver: ((_ newValue: SomeTime?) -> Void)?

    var chooseCAlertReturnsEngGrk: SomeType? = nil {
        didSet {
            chooseCAlertReturnsEngGrkObserver?(chooseCAlertReturnsEngGrk)
        }
    }
}