SwiftでiPhoneとiPadを判別する ref: http://qiita.com/osamu1203/items/f45909bdffcf6373f4b6

file0.swift

enum UIUserInterfaceIdiom : Int {
    case Unspecified

    case Phone // iPhone and iPod
    case Pad // iPad
}

file1.swift

if UIDevice.currentDevice().userInterfaceIdiom == .Phone {
    println("iPhone")
}else if UIDevice.currentDevice().userInterfaceIdiom == .Pad{
    println("iPad")
}else{
    println("Unspecified")
}