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Sorting an array of optional elements that contains another option

How can I sort the options array that contains 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]

How can I sort the array based on dateCompleted?

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1 answer


Your sort function can use a combination of the optional chaining and the null 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
}

This sorts the items in value dateCompleted

and all items that are nil

, and items with are dateCompleted == nil

considered "in the distant past" so that they are ordered before all other items.



Update for Swift 3 (assuming that dateCompleted

is 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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