如何使用Xcode10.2.1/swift 4.2中的'iterateEnum‘函数按照枚举列表中指定的特定顺序对数组中的字符串值进行排序

Question

作为从swift 3.0 xcode 9.4.1到swift 4.2 xcode 10.2.1的代码迁移的一部分，我面临着swift 3.0中使用的数组排序方法的问题，该方法在swift 3.x中工作得很好，但在xcode 10.2.1/swift 4.2上不能工作，返回nil值而不是排序的数组列表：

// Statuses currently come through in an array, which is not sorted in the correct order
// The order is specific, as specified in the enum list
// Create a pre-made list of section headers, only for statuses that have valid activities

Leave是一个JSONEncodable模式类，状态是在其中声明的枚举字符串。任何帮助都将不胜感激。提前谢谢。

open class Leave: JSONEncodable {

    public enum Status: String { 
        case Drafts = "Drafts"
        case PushedBack = "Pushed Back"
        case PendingApproval = "Pending Approval"
        case UpcomingLeave = "Upcoming Leave"
        case History = "History"
        case Booked = "Booked"
        case Approved = "Approved"
        case Denied = "Denied"
        case ApprovedAndDeniedRequest = "Approved and Denied Request"
        case Error = "Error"
    }
}

var orderedSections: [Leave.Status] {
    var list: [Leave.Status] = []
    for status in iterateEnum(Leave.Status.self) {
        list.append(status)
    }
    return list
}


fileprivate func iterateEnum<T: Hashable>(_: T.Type) -> AnyIterator<T> {
    var i = 0
    return AnyIterator {
        let next = withUnsafePointer(to: &i) { $0.withMemoryRebound(to: T.self, capacity: 1) { $0.pointee } }
        let res: T? = next.hashValue == i ? next : nil
        i += 1
        return res
    }
}

Answer 1

尝试以下操作：

var orderedSections: [Leave.Status] {
    var list: [Leave.Status] = []

    Leave.Status.allCases.forEach { (status) in
       list.append(status)
    }
//    for status in iterateEnum(Leave.Status.self) {
//        list.append(status)
//    }
    return list
}

Answer 2

你不需要iterateEnum函数，只需在String之后使你的enum符合CaseIterable协议，就可以访问.allCases.

示例：

public enum Listing: String, CaseIterable {
    case a = "a"
    case b = "b"
}

Listing.allCases.forEach({print($0)})