How to combine two sorting methods in Swift?

Question

Here is a sorting problem that I faced during working on Swift 3. I have an Array with many objects called Feed as follows. The sorting method should include 2 steps: - The objects having the same barcode will stand side-by-side in the array - The object having the same barcode having the status A will stand on the left, the next is the one having status B, then the one with status C.

How to write a sort function to cover those two steps ??

class Feed: Object {

    dynamic var barcode: Int
    dynamic var feed_type = ""

    dynamic var status: String 

    override class func primaryKey() -> String {
        return "id"
    }

    var type: FeedType {
        get {
            return FeedType.get(feed_type)
        }

        set(newValue) {
            feed_type = newValue.key
        }
    }

}

@Sulthan: Ops my bad. I edited the code

Nam Doan
– Nam Doan

2017-03-17 10:28:59 +00:00
Commented Mar 17, 2017 at 10:28 — Nam Doan
– Nam Doan, Commented Mar 17, 2017 at 10:28

Sulthan · Accepted Answer · 2017-03-17 10:50:11Z

1

You can simply chain up the comparison:

let values: [Feed] = ...

let sortedValues: [Feed] = values.sorted { (feed1, feed2) in
    feed1.barcode < feed2.barcode
    || (feed1.barcode == feed2.barcode && feed1.status < feed2.status)
}

Since you are using Objective-C objects, you could also use the old NSSortDescriptor. However, it was not bridged to Swift therefore you need some casting magic:

let barcodeSortDescriptor = NSSortDescriptor(key: "barcode", ascending: true)
let statusSortDescriptor = NSSortDescriptor(key: "status", ascending: true)

let sortedValues: [Feed] = (values as NSArray)
    .sortedArray(using: [barcodeSortDescriptor, statusSortDescriptor]) as! [Feed]

This is especially useful when your sorting is more complicated.

edited Mar 17, 2017 at 10:50

answered Mar 17, 2017 at 10:33

Sulthan

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Comments

Apurv · Accepted Answer · 2017-03-17 10:32:15Z

1

So in your comparator method you should receive 2 objects. Now do the following stuff.

if(object1.barcode > object2.barcode)
    return false;
else if(object1.barcode < object2.barcode)
    return true;
else {
    if(object1.status > object2.status)
        return false;
    else
        return true;
}

answered Mar 17, 2017 at 10:32

Apurv

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1 Comment

Nam Doan Over a year ago

hi @Apurv, I'm a newbie working on Sorting in Swift 3. Could you please give an example of receiving 2 objects in the comparator method? Thanks

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