NSTextAlignment can not be represented in Objective-C

Question

In my Swift class, I exposed an variable to objective c by defining it as

@objc var textAlignment: NSTextAlignment? {
    didSet {
        if textAlignment != nil {
            label.textAlignment = textAlignment!
        }
    }
}

And it is Wrong! because compiler complains that it is not a type that can be represented in Objective-C.

---

But the followings are right

var textAlignment: NSTextAlignment? {
    didSet {
        label.textAlignment = textAlignment!
    }
}

Or

@objc var textAlignment: NSTextAlignment {
    didSet {
        label.textAlignment = textAlignment
    }
}

So it looks like if I expose the method to objective-C, It can not be optional value. However if I use it internally, I can! Is it because it is a scalar value where in Objective-C we have no way to represent it as nil?

My intention was just want to make it not compulsory.

Answer 1

NSTextAlignment is an enum, not an class - the textAlignment variable can't be mapped as optional to objective c because that would require it to be a pointer to an object type.

Try:

@objc var textAlignment: NSTextAlignment { 
  ...
}

Or, if you really need it to be optional, you could expose it to Objective C as an NSNumber, wrapping the textAlignment.rawValue or setting to nil when no value is needed.