iOS - 类型'DispatchQueue'没有成员'GlobalAttributes'

Question

我有以下错误：

  

类型'DispatchQueue'没有成员'GlobalAttributes'

在我的代码中。你知道为什么吗？

 public typealias Classification = (Label: DigitLabel, Confidence: CGFloat, BestPrototypeIndex: Int)
    public func classifyDigit(digit: DigitStrokes, votesCounted: Int = 5, scoreCutoff: CGFloat = 0.8) -> Classification? {
        if let normalizedDigit = normalizeDigit(inputDigit: digit) {
            let serviceGroup = DispatchGroup()
            let queue = ***DispatchQueue.global(attributes: DispatchQueue.GlobalAttributes.qosUserInitiated)***
            let serialResultsQueue = DispatchQueue(label: "collect_results")

            var bestMatches = SortedMinArray<CGFloat, (DigitLabel, Int)>(capacity: votesCounted)
            for (label, prototypes) in self.normalizedPrototypeLibrary {

                queue.async(group: serviceGroup) {
                    var localBestMatches = SortedMinArray<CGFloat, (DigitLabel, Int)>(capacity: votesCounted)
                    var index = 0
                    for prototype in prototypes {
                        if prototype.count == digit.count {
                            let score = self.classificationScore(sample: normalizedDigit, prototype: prototype)
                            //if score < scoreCutoff {
                            localBestMatches.add(value: score, element: (label, index))
                            //}
                        }
                        index += 1
                    }
                    serialResultsQueue.async(group: serviceGroup) {
                        for (score, bestMatch) in localBestMatches {
                            bestMatches.add(value: score, element: bestMatch)
                        }
                    }
                }
            }

我还附上the file，以防万一。

Answer 1

根据Apple's documentation，消息是正确的。

也许你想使用DispatchQueue.Attributes？

修改

我只是仔细看了一下文档：

DispatchQueue.global()似乎有所改变。文档显示了这个声明：

class func global(qos: DispatchQoS.QoSClass = default) -> DispatchQueue

我测试了一些变体，Xcode提出并找到了这一行：

let queue = DispatchQueue.global(qos: DispatchQoS.QoSClass.userInitiated)

  

我没有测试，如果这对你的例子100％有用，但Xcode会编译它