arrays - 对包含另一个可选项的可选项数组进行排序

Question

如何对包含可选 NSdate 的可选数组进行排序？

class HistoryItem {
   var dateCompleted: NSDate?
}

let firstListObject = someListOfObject.last
let secondListObject = someOtherListOfObject.last
let thirdListObject = evenSomeOtherListOfObject.last //Last returns 'T?'

var array = [firstListObject , secondListObject, thirdListObject]

如何根据完成日期对数组进行排序？

Answer 1

您的排序函数可以结合使用可选链和 nil合并运算符:

sort(&array) {
    (item1, item2) -> Bool in
    let t1 = item1?.dateCompleted ?? NSDate.distantPast() as! NSDate
    let t2 = item2?.dateCompleted ?? NSDate.distantPast() as! NSDate
    return t1.compare(t2) == NSComparisonResult.OrderedAscending
}

这将根据 dateCompleted 值对项目进行排序，并且所有项目是 nil 并且带有 dateCompleted == nil 的项目被视为“在遥远的过去”以便它们在所有其他项目之前被订购。

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Swift 3 的更新(假设 dateCompleted 是一个 Date):

array.sort { (item1, item2) -> Bool in
    let t1 = item1?.dateCompleted ?? Date.distantPast
    let t2 = item2?.dateCompleted ?? Date.distantPast
    return t1 < t2
}