Using NSMutableArray sortUsingFunction in Swift?

Question

This link tells you what your sorting function has to look like, but I just can't make a Swift function look like that.

Here's my call:

packetsArray.sortUsingFunction(comparePacketDates, context: nil)

Here's my function, and I've tried a zillion other variations of it:

static func comparePacketDates(packet1 : AnyObject, packet2: AnyObject, context: UnsafeMutablePointer<Void>) -> Int {

And I've tried using a c function instead, this and a few other variations:

NSInteger comparePacketDates(id packet1, id packet2, void* dummy);

It's always "cannot invoke with argument list ..." saying the function isn't what's expected as the first argument.

Does anyone have example code of a Swift function that would be accepted as the first argument of the Swift sortUsingFunction? Or even a c function that would be accepted as the first argument of the Swift SortUsingFunction?

I think the body of your swift comparePacketDates function is missing. That might be helpful in diagnosing the problem. Also, you might consider just casting the NSMutableArray to a Swift array and using Swift's sorting mechanisms. See here: stackoverflow.com/questions/25837539/… — btmcnellis
– btmcnellis, Commented Nov 4, 2015 at 3:52
The body of my comparePacketDates doesn't matter, because it's not getting that far. It won't accept the way I've declared it as the first argument in sortUsingFunction. Also if I did caste it to a Swift Array does Swift's sort work for an array of custom objects? Or does it just sort arrays of strings and numbers? — Joe C
– Joe C, Commented Nov 4, 2015 at 14:38

rob mayoff · Accepted Answer · 2015-11-04 05:28:28Z

4

Use sortUsingComparator. It's simpler than sortUsingFunction. Here's the syntax:

a.sortUsingComparator {
    let packet1 = $0 as! Packet
    let packet2 = $1 as! Packet
    if packet1.timestamp < packet2.timestamp {
        return .OrderedAscending
    }
    if packet1.timestamp == packet2.timestamp {
        return .OrderedSame
    }
    return .OrderedDescending
}

answered Nov 4, 2015 at 5:28

rob mayoff

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Comments

Shripada · Accepted Answer · 2015-11-04 04:23:28Z

0

Here is an example for your reference that I wrote:

var ma = NSMutableArray()

ma.addObject("Hi")
ma.addObject("Anil")

func comp(first: AnyObject, second:AnyObject,  context: UnsafeMutablePointer<Void>) -> Int {
  let f:String  = first as! String
  let s:String = second as! String

  if f > s {
    return 1
  }
  else if ( f == s ) {
    return 0
  }

  return -1

}

ma.sortUsingFunction(comp, context:UnsafeMutablePointer<Void>(bitPattern: 0))

HTH, as a reference to you. Note: I am in Xcode 7.1 Swift 2.1.

answered Nov 4, 2015 at 4:23

Shripada

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2 Comments

Joe C Over a year ago

This did not work using what I have: XCode 6.4 / Swift 1.2. Same old "cannot invoke". Maybe it's time I upgraded.

Joe C Over a year ago

I'll bet your solution works in Swift 2.1 but I cannot test it for a while as I was going to upgrade in 2 weeks. I don't normally like the "do it a different way" answers, but rob mayor's solution is working for me so I have to accept his answer. Thx a lot though.

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