对包含另一个可选项目的可选项目数组进行排序 [英] Sort an array of optional items that holds yet another optional

问题描述

如何对包含可选 NSdate 的可选数组进行排序?

How can I sort an array of optionals that holds an optional NSdate?

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 dateCompleted 对数组进行排序?

How can I sort array based on dateCompleted?

推荐答案

您的排序函数可以使用可选链和 nil 的组合合并运算符:

Your sort function could use a combination of optional chaining and the nil coalescing operator:

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
}

这将对 dateCompleted 值上的项目进行排序，以及所有符合是 nil 并且带有 dateCompleted == nil 的项目被视为在遥远的过去"以便在所有其他项目之前订购它们.

This would sort the items on the dateCompleted value, and all items that are nil and items with dateCompleted == nil are treated as "in the distant past" so that they are ordered before all other items.

Swift 3 的更新(假设 dateCompleted 是 Date):

Update for Swift 3 (assuming that dateCompleted is a Date):

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

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