casting.swift

//import Foundation
//class P: NSObject {}

protocol P {}
class C: P {}

extension SequenceType
{
    func mapAs<T>(type: T.Type) -> [T] {
        return map { $0 as! T }
    }
}

func doStuffWith(seq: AnySequence<AnyObject>) {
    
    let a1 = Array(seq).map { $0 as! P } // works
    let a2 = seq.map { $0 as! P } // works
//    let a3 = Array(seq) as! [P] // works from AnyObject->P(a class), but doesn't work for Any->P or if P is a protocol
    let a4 = seq.mapAs(P) // works! same as #2 really
}


let objs: [AnyObject] = [C(), C(), C()]

let things = AnySequence(objs) // AnySequence<AnyObject>

doStuffWith(things)