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

Question

我有以下错误:

Type 'DispatchQueue' has no member '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)
                        }
                    }
                }
            }

我还附上了the file ，以防万一。

Answer 1

根据 Apple's documentation , 消息是正确的。

也许您想使用 DispatchQueue.Attributes？

编辑:

我刚刚仔细查看了文档:

DispatchQueue.global() 似乎已更改。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)

I did not test, if this works 100% with your example, but Xcode will compile it