Swift: Sort NSArray of CGPoints by one value, then another?

Question

I'm trying to sort an NSArray of CGPoints (describing a CGPath) by their y values (descending), then by their x values (ascending). This is what I have so far (Swift code):

var anglePoints:[CGPoint] = [CGPoint(x: 0, y: 0), CGPoint(x: 32, y: 32), CGPoint(x: 32, y: 0)]

anglePoints.sort { $0.0.y > $0.1.y }

// anglePoints is now equal to [CGPoint(x: 32, y: 32), CGPoint(x: 32, y: 0), CGPoint(x: 0, y: 0)]

Obviously, sorting on x after this will result in the y values no longer being in order.

Is there a way to perform both sorts in a single call? Something like Linc's OrderBy().ThenBy()?

`anglePoints.sort { if $0.0.y != $0.1.y { return $0.0.y > $0.1.y } return $0.0.x < $0.1.x }` — The Paramagnetic Croissant, Feb 18 '15 at 09:55
Hmm, that's just acting the same as sorting the array twice (anglePoints is now equal to `[CGPoint(x: 0, y: 0), CGPoint(x: 32, y: 32), CGPoint(x: 32, y: 0)]`... — MassivePenguin, Feb 18 '15 at 09:56
@MassivePneguin no, it's not. If it is, then you did something wrong when copying the code. — The Paramagnetic Croissant, Feb 18 '15 at 09:57
Looks like your code was changed between when you originally posted it and when I answered... — MassivePenguin, Feb 18 '15 at 10:00
I deleted my original comment because I misread the requirements. I was referring to my new comment – sorry if that was confusing. — The Paramagnetic Croissant, Feb 18 '15 at 10:14

Antonio · Accepted Answer · 2015-02-18T10:21:15.090

1

You can do that with a single sort:

anglePoints.sort { $0.0.y != $0.1.y ? $0.0.y > $0.1.y : $0.0.x < $0.1.x }

which can be more explicitly written as:

anglePoints.sort {
    if $0.0.y != $0.1.y {
        return $0.0.y > $0.1.y
    } else {
        return $0.0.x < $0.1.x
    }
}

Translated in words: if the y coordinates are different, sort by y, otherwise by x

edited Feb 18 '15 at 10:21

answered Feb 18 '15 at 09:55

Antonio

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the second criterion should be `$0.0.x < $01.x` since x values should be sorted in ascending order. – The Paramagnetic Croissant Feb 18 '15 at 09:56

Swift: Sort NSArray of CGPoints by one value, then another?

1 Answers1