Can a Swift init be made available only for ObjectiveC?

Question

Suppose I have a Swift class

@objcMembers class C: NSObject {
  let range: ClosedRange<Int>

  init(range: ClosedRange<Int>) {
    self.range = range
    super.init()
  }

  convenience init(min: Int, max: Int) {
    self.init(range: min...max)
  }
}

Is there a way to make the convenience init available only from Objective-C, so that the API will be smaller?

Answer 1

You can expose the method to Objective-C runtime and make it private at the same time. This however requires you to introduce the private method's interface yourself (ideally by extending the auto-generated interface, rather than introducing a separate class declaration). Your swift class should look something like this:

@objc(TDWSwiftObject)
class SwiftObject: NSObject {

    let range: ClosedRange<Int>

    init(range: ClosedRange<Int>) {
        self.range = range
        super.init()
    }

    @objc private convenience init(min: Int, max: Int) {
        self.init(range: min...max)
    }

}

And then add the missing Objective-C parts as a class category:

@interface TDWSwiftObject (Private)

- (instancetype)initWithMin:(int)min max:(int)max;

@end

Now your Swift code won't be able to refer to the constructor (because it has private access modifier), while the Objective-C code can use it just fine.