Swift sort array of objects based on boolean value

Question

I'm looking for a way to sort a Swift array based on a Boolean value.

I've got it working using a cast to NSArray:

var boolSort = NSSortDescriptor(key: "selected", ascending: false)
var array = NSArray(array: results)
return array.sortedArrayUsingDescriptors([boolSort]) as! [VDLProfile]

But I'm looking for the Swift variant, any ideas?

Update Thanks to Arkku, I've managed to fix this using the following code:

return results.sorted({ (leftProfile, rightProfile) -> Bool in
    return leftProfile.selected == true && rightProfile.selected != true
})

re. update in the question, comparing booleans with true is unnecessary clutter, and it would be better Swift style to omit the () around the closure (as is permitted when the closure is the last argument). — Arkku
– Arkku, Commented Nov 21, 2015 at 16:25

Arkku · Accepted Answer · 2022-09-16 14:44:02Z

186

Swift's arrays can be sorted in place with sort or to a new array with sorted. The single parameter of either function is a closure taking two elements and returning true if and only if the first is ordered before the second. The shortest way to use the closure's parameters is by referring to them as $0 and $1.

For example (to sort the true booleans first):

// In-place:
array.sort { $0.selected && !$1.selected }

// To a new array:
array.sorted { $0.selected && !$1.selected }

(edit: Updated for Swift 3, 4 and 5, previously sort was sortInPlace and sorted was sort.)

edited Sep 16, 2022 at 14:44

answered Feb 28, 2015 at 11:29

Arkku

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2 Comments

Antoine Over a year ago

Thanks, using your answer I've managed to fix this in Swift. I've updated my question with the answer.

Andrew Ho Over a year ago

Please note that in Swift 3.0 .sort is used

Teemu Kurppa · Accepted Answer · 2015-11-23 07:44:51Z

5

New (for Swift 1.2)

return results.sort { $0.selected && !$1.selected }

Old (for Swift 1.0)

Assuming results is of type [VDLProfile] and VDLProfile has a Bool member selected:

return results.sorted { $0.selected < $1.selected }

See documentation for sorted

edited Nov 23, 2015 at 7:44

answered Feb 28, 2015 at 11:38

Teemu Kurppa

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1 Comment

Antoine Over a year ago

This gave me an error: Cannot invoke 'sorted' with an argument list of type.

saurabh · Accepted Answer · 2015-02-28 11:34:44Z

-1

Swift’s standard library provides a function called sorted, which sorts an array of values of a known type, based on the output of a sorting closure that you provide

reversed = sorted(array) { $0 > $1 }

reversed will be a new array which will be sorted according to the condition given in the closure.

answered Feb 28, 2015 at 11:34

saurabh

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1 Comment

atultw Over a year ago

This doesn't answer the question - OP needs to sort by boolean values which cannot be compared using > or <. (also the first sentence is copied word for word from the Swift book)

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