Can a Swift Optional Int (Int?) be exposed to Objective-C via bridging?

Question

Within a Swift class derived from an Obj-C based framework (but could just as easily be a Swift class with an @objc attribute) I declare two stored properties:

var optInt: Int? var optString: String? 

Only optString is being exposed to Obj-C via the generated -Swift.h header.

String? is presumably fine because it is exposed using an NSString object which can be nil, so the bridging has a way to represent no value.

If I remove the ? from optInt it's exposed with an NSInteger type, so I can see that for non-optional integers it avoids objects and bridges value type to value type, but does this literally mean that an Int? can't be exposed?

I can't seem to find any documentation that explicitly says this is the case. There is a whole list of incompatible Swift features here that this doesn't appear on: Using Swift from Objective-C

The use case here is the classic situation requiring the passing of a numeric ID which could legitimately be zero. In the pre-Swift world NSNumber and nil is exactly how I went about implementing this, but it just feels wrong to be trying to migrate a class to Swift but then hanging on to Obj-C types within the Swift class specifically for this reason.

I suppose I had envisaged that an Int? unlike Int would bridge as an NSNumber in the background, with its potentially nil value feeding the "has no value" element of the optional in Swift.

Is there anything I'm missing here? To reiterate, can a Swift Optional Int (Int?) be exposed to Objective-C via bridging?

Answer 1

Here's a concrete answer for the solution described above:

private var _number: Int? public var number: NSNumber? {     get {         return _number as NSNumber?     }     set(newNumber) {         _number = newNumber?.intValue     } }  // In case you want to set the number in the init public init(number: NSNumber?) {     _number = number?.intValue }