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的选项数组进行排序？

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dateCompleted对数组进行排序？

Answer 1

您的排序函数可以使用可选链接和零合并运算符的组合:

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,并将所有项目nil和项目dateCompleted == nil视为"在遥远的过去",以便在所有其他项目之前对它们进行排序.

更新Swift 3(假设dateCompleted是a Date):

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