foo.swift

import Foundation


func checkIt(nameString: String, dictionary: [String: String]) -> Bool
{
    let namePieces = nameString.componentsSeparatedByString("/")
    
    guard namePieces.count > 2,
          let urlString = dictionary["url"],
          url = NSURL(string: urlString),
          _ = dictionary["itag"],
          type = dictionary["type"]
          where type.containsString("video/mp4")
    else
    {
        return false
    }
    
    url // outputs the correct URL in playground
    
    return true
}

let dict = ["url": "http://domain/file", "itag": "bla", "type": "video/mp4"]

checkIt("/something/bla.mp4", dictionary: dict)