class Pokemon: CustomDebugStringConvertible {
  let name: String
  init(name: String) {
    self.name = name
  }
  var debugDescription: String { return "\(name)>" }
  deinit { print("\(self) escaped!") }
}

func delay(seconds: Int, closure: ()->()) {
  let time = DispatchTime.now() + .seconds(seconds)
  DispatchQueue.main.after(when: time) {
    print("🕑")
    closure()
  }
}

func demo1() {
  let pokemon = Pokemon(name: "Mewtwo")
  print("before closure: \(pokemon)")
  delay(1) {
    print("inside closure: \(pokemon)")
  }
  print("bye")
}

before closure: <Pokemon Mewtwo>
bye
🕑
inside closure: <Pokemon Mewtwo>
<Pokemon Mewtwo> escaped!

var name = "John"

let test1 = {
    print(name)
}

name = "Aby"

test1()

var name = "John"

let test1 = {
    name = "Jack"
    print(name)
}

name = "Aby"

test1()

var str = "Hello, playground"
let show1 = { [strcopy = str] in
// 在闭包一开始创建的时候捕获变量的值，
// []内的为捕获列表，一开始捕获值，而非引用。
// 捕获的为原始变量的副本->常量，并且只能在闭包内访问

    print("这是str-----\(str)\n这是strcopy-----\(strcopy)")
}

str = "hello"

show1()

这是str-----hello
这是strcopy-----Hello, playground

var str = "Hello, playground"
let show1 = { [str] in
    print(str)
}

func demo6_equivalent() {
  var pokemon = Pokemon(name: "Pikachu")
  print("before closure: \(pokemon)")
  // here we create an intermediate variable to hold the instance
  // pointed by the variable at that point in the code:
  let pokemonCopy = pokemon
  delay(1) {
    print("inside closure: \(pokemonCopy)")
  }
  pokemon = Pokemon(name: "Mewtwo")
  print("after closure: \(pokemon)")
}