How do I check if a var is a Tuple in Swift?

Question

Reading the Type Casting section of the Swift Guide I see I use the is keyword to type check variables.

func isString(test: AnyObject?) -> Bool {
    return test is String
}

It seems when I try something similar to check for a Tuple containing three NSNumber objects, I receive a 'Tuple does not conform to protocol AnyObject'. Is there any way to check if a variable contains a Tuple?

func isTuple(test: AnyObject?) -> Bool {
    return test is (NSNumber, NSNumber, NSNumber) // error
}

Answer 1

You can't use AnyObject here because a tuple is not an instance of a class type.

• AnyObject can represent an instance of any class type.
• Any can represent an instance of any type at all, including function types.

_{From The Swift Programming Guide - Type Casting}

Instead, try using the more general Any type:

func isTuple(test: Any?) -> Bool {
    return test is (NSNumber, NSNumber, NSNumber)
}

isTuple("test") // false
let tuple: (NSNumber, NSNumber, NSNumber) = (Int(), Int(), Int())
isTuple(tuple) // true