7.闭包

sort 函数

func backward(a:Int, b:Int) -> Bool {

return a > b

}

let arr = [1,5,2,4,3,7]

var brr = arr.sort(backward)

闭包表达式语法

brr = arr.sort({ (a:Int, b:Int) -> Bool in

return a < b

})

brr.sort({a, b in return a > b})

brr.sort({a, b in a > b})

brr.sort({$0 > $1})

brr.sort(){$0 > $1}

map

var arr = [16, 58, 510]

let str = arr.map {$0 + 30}

捕获值

func a_f(a: Int) -> ()->Int {

var sum = 0

func b_f() ->Int {

sum += a

return sum

}

return b_f

}

let s1 = a_f(10)

s1()  // 10

s1()  // 20

let s2 = s1

s2()  // 30

闭包是引用类型