Declare “NSMapTable StrongObject” in Swift 3

Question

How can I declare an NSMapTable in Swift 3? Why doesn\'t this example from Apple work?

let activeLines = NSMapTable.strongToStrongObjectsMapTable()
         


        

Answer 1

NSMapTable.strongToStrongObjects() will fail with the error:

error: generic parameter 'KeyType' could not be inferred
NSMapTable.strongToStrongObjects()
           ^

The class declaration of NSMapTable is:

open class NSMapTable<KeyType : AnyObject, ObjectType : AnyObject> : NSObject, NSCopying, NSCoding, NSFastEnumeration

You need to specify the key and object types of your map table in its declaration:

NSMapTable<NSObject, NSObject>.strongToStrongObjects()