externvoid

var a: Any? = nil
a = 2
//a = 2.0                                                                       
let b = a as? Int //可能ならOptionalへ、失敗ならnil
let c = a as! Int?
//let d = a as Int? compile error!!
let d = a as? Int?
//let e = a! // forced unwrap
print(b)
print(c)

externvoid

asの用途
1. 乗り継ぎタイプへのキャスト、即値から参照値へ変換、Swiftで導入された構造体からFoundationで定義されたクラスへ変換。
string -> nsstring
array -> NSArray
dictionary -> nsdictionary
// Brigded type casting
    let string = "3"
    let nsString = string as NSString
    let value = nsString.floatValue // 3
逆は、クラスのコンストラクタで可能。例：NSString(string: "Convertion")

externvoid

class Bar {
  let someVal = 5
  lazy var g:() -> String =  { [unowned self] in
// lazy: 次のエラー対策：error: use of unresolved identifier 'self'
    return String(self.someVal)
  }
}
var bar = Bar()
print(bar.g()) // string "5"     

externvoid

// nilが返るかもしれないメソッドの取り扱い
//let obj6 = NSUserDefaults.standardUserDefaults().objectForKey("user data")
var obj6: AnyObject? = nil
print(obj6)
var obj5   = obj6 as? [String: Int] ?? [String: Int]()
//var obj5: [String: Int] = obj! as [String: Int] ?? [String: Int]()
obj5["hp"] = 3
print(obj5) // ["hp": 3]                                                        
print(obj5.dynamicType) // Dictionary<String, Int>

externvoid

nilを返すかもしれないメソッドから値を受け取る。
例：objectForKeyはAnyObject?を返す！！

[String: Int]?を[String: Int]へキャストする。

import Foundation
var obj: [String: Int]? = ["hp": 0]
print(obj) 
var obj3: [String: Int] = obj! as [String: Int] ?? [String: Int]()

externvoid

class MyClass {
  var x: Int = 10
  func method() {
    print("x = \(x)")
  }
  var g:()->() = {                                                              
    let y = self.x
    print(__LINE__,"行", String(self.dynamicType), __FUNCTION__)
    print("y = \(y)")
  }

externvoid

var a = 0                                                                       
var b = 0

let closure0 = { [a] (b:Int)->Void in
// capture list, argument listの同時記述が出来る。
  print(a, b)
}

a = -1
b = 99

externvoid

var ar2:Array<NSString> = ["aaa", "bbb", "abc",]
var strings:NSMutableArray = NSMutableArray(array: ar2)

print(strings)

strings.sortUsingComparator( {
    return $1.compare($0 as String)                             
} )
//error: 'AnyObject' is not convertible to 'String'; did you mean to use 'as!' to force downcast?
//    return $1.compare($0 as String)

externvoid

import Foundation

func iterateEnum<T: Hashable>(_: T.Type) -> AnyGenerator<T> {
    var cast: (Int -> T)! // reference to clousure
//print(($0).dynamicType)
// what is $0 ?, Int, 0, 1, 2, 3, 4 for nil
    switch sizeof(T) {
    case 0: return anyGenerator(GeneratorOfOne(unsafeBitCast((), T.self)))
    case 1: cast = { unsafeBitCast(UInt8(truncatingBitPattern: $0), T.self) }
// print($0.dynamicType);print($0)

externvoid

import Foundation                                                               
var dateFmt: NSDateFormatter = NSDateFormatter()
dateFmt.dateFormat = "yyyy/MM/dd HH:mm:ss"

let date1 = dateFmt.dateFromString("2014/03/18 00:00:00")!
let date2: NSDate = dateFmt.dateFromString("2014/03/19 00:00:00")!

var order = date1.compare(date2)
print(order)
print(order == NSComparisonResult.OrderedDescending)