Using sortedArrayUsingSelector in Swift

Question

Hey people of stackoverflow,

I have implemented this class in swift:

class PCCountedColor {

    var color:UIColor
    var count:Int

    init (color:UIColor, count:Int)
    {
        self.color = color;
        self.count = count;
    }

    func compare(object:PCCountedColor) -> NSComparisonResult
    {
        if ( self.count < object.count )
        {
            return NSComparisonResult.OrderedDescending
        }
        else if ( self.count == object.count )
        {
            return NSComparisonResult.OrderedSame
        }

        return NSComparisonResult.OrderedAscending
    }
}

Then I have an NSMutableArray which is being filled with objects of above class:

var sortedColors:NSMutableArray = []
var container:PCCountedColor = PCCountedColor(color:curColor, count: colorCount)
sortedColors.addObject(container)

After which I try to have that array sorted via a special function in the above class:

sortedColors.sortedArrayUsingSelector(Selector("compare:"))

But all I get is an error:

SwiftColorArt[1584:42892] *** NSForwarding: warning: object 0x7fd391b25a50 of class 'SwiftColorArt.PCCountedColor' does not implement methodSignatureForSelector: -- trouble ahead Unrecognized selector -[SwiftColorArt.PCCountedColor compare:]

I am new to Swift and have already checked Apple's official documentation which can be found here.

I have tried several syntax variants (adding ":" or remove them, pass the function name as a string or not ... as well as various combinations) but none of them helped.

So in my desperation I turn to you for help.

Best regards,

Jan

Probably the same issue as here: stackoverflow.com/questions/24415662/… . — Martin R
– Martin R, Commented Jan 7, 2015 at 19:38

matt · Accepted Answer · 2015-01-07 19:59:54Z

3

"SwiftColorArt.PCCountedColor' does not implement methodSignatureForSelector: -- trouble ahead Unrecognized selector -[SwiftColorArt.PCCountedColor compare:]"

The error message tells you what to do. Make this class a subclass of NSObject and all will be well.

answered Jan 7, 2015 at 19:59

matt

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7 Comments

akashivskyy Over a year ago

To be fair, it doesn't literally tell that... :P

matt Over a year ago

Okay, well, it tells me what to do. :) But really, I agree with you, @akashivskyy - the OP should not be calling this method in the first place, if it can be avoided. Swift has excellent native facilities for sorting an array.

Jan Over a year ago

Thanks - that helped ! I am currently trying to learn swift by porting github.com/fleitz/ColorArt (which is written in Objective-C, which I also don't know) to swift. @akashivskyy - I will make sure to look into that !

akashivskyy Over a year ago

Good luck! Make sure to watch some WWDC sessions, they're a great learning resource for beginners.

matt Over a year ago

@JanGregorTriebel What you're doing is the same sort of thing I did when I was learning. First, I translated my existing apps very literally from Objective-C to Swift. Then I rearchitected them to make them more Swifty.

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