Annotate NSArray * in Objective-C so that it is bridged to Array

Question

Is there a way to annotate an NSArray of NSNumber:

@property (nonatomic) NSArray<NSNumber *> *myProperty

in Objective-C, so that it will be imported in Swift as

var myProperty: [Int] instead of var myProperty: [NSNumber]?

I know of NS_SWIFT_NAME, but that does not allow changing the type.

Can you explain more clearly? Do you need an `Int` array or `NSNumber` array in swift? Or maybe an `Int` array in Objective c? — trungduc, Oct 29 '17 at 06:29
After asking the question I researched a little more. I don't think it's possible. If you look at the `allowedTouchTypes` property of `UIGestureRecognizer`. That one is also an `NSArray *` return type, and is imported in Swift as `[NSNumber]`. — Trenskow, Oct 29 '17 at 07:00
@Trenskow you can get any element from your number array `[NSNumber]` and access its `intValue` property which will return an `Int`. You can also map all elements `numbers.map{$0.intValue}` will return an array of Int `[Int]` — Leo Dabus, Oct 29 '17 at 07:06
@Trenskow If you are working with NSArray you would need to cast from `Any` to `NSNumber` `numbers.flatMap{($0 as? NSNumber)?.intValue}`. But you should work with Swift native Array type — Leo Dabus, Oct 29 '17 at 07:12
Yes. I'm designing an API, and I would like this to be automatically imported as this in Swift, but I know now, that it is not possible. — Trenskow, Oct 29 '17 at 08:19

score 2 · Accepted Answer · answered Oct 29 '17 at 07:26

2

Unfortunately you can't change the static type when importing a symbol from Objective-C.

But you can assign a Swift Int array without any type cast (assuming foo is an instance of the ObjC class). However the type doesn't change.

foo.myProperty = [1, 2, 3, 4, 5]
print(type(of: foo.myProperty)) // Optional<Array<NSNumber>>

On the other hand to get a distinct [Int] type you have to cast the type

let mySwiftProperty = foo.myProperty as! [Int]
print(type(of: mySwiftProperty)) // Array<Int>

answered Oct 29 '17 at 07:26

vadian

I accept this as the correct answer. After the initial question I did some research, and even UIKit does this, so I guess it's not possible. I just wanted not to make it my users responsibility to cast it to the correct type. Thanks! – Trenskow Oct 30 '17 at 15:04

1 Answers1