Swift: Pass Type as Parameter

Question

Is it possible to pass in a Type as a function parameter in Swift? Note: I do not want to pass in an object of the specified type, but instead the Type itself. For example, if I wanted to replicate Swift's as? functionality:

infix operator <-? { associativity left }
func <-? <U,T>(x:U?, t:T) -> T? {
  if let z = x as? t {
      return z
    }
  }
}

Of course, t is being pass in as a type, but I would like to pass in the Type itself so I can check against that type in the function body.

Answer 1

You can use T.Type, but you have to cast as T and not t:

infix operator <-? { associativity left }
func <-? <U,T>(x:U?, t:T.Type) -> T? {
    if let z = x as? T {
        return z
    }
    return nil
}

Sample usage:

[1,2, 3] <-? NSArray.self // Prints {[1, 2, 3]}
[1,2, 3] <-? NSDictionary.self // Prints nil