swift closure闭包

//闭包的几种书写方式

var names = [13,345,2,323,1,8,21,42,34,32,42,1]


// 1
func compares(args: Int, args2: Int) ->Bool {
return args > args2
}
var names2 = names.sort(compares)
print(names2)

 


// 2
names2 = names.sort({(args: Int, args2: Int) -> Bool in 
return args < args2
})
print(names2)


// 3

names2 = names.sort({$0 > $1})
print(names2)

func customer_fn(cu_fn: ()-> String) {
let str: String = cu_fn()
print("customer accpect args for closure : (str)")
}
customer_fn({" this is closeure "})

//autoclosure
func customer_fn(@autoclosure cu_fn: ()-> String) {
let str: String = cu_fn()
print("customer accpect args for closure : (str)")
}
customer_fn(" this is closeure2 ")


//4 此种情况比较特殊，只适用于一句表达式，做比较操作，才可用
names2 = names.sort(>)
print(names2)

 

//尾随闭包

//使用场景：需要传入一个闭包，并且为最后一个参数时
names2 = names.sort() { $0 > $1}
print(names2)

//使用场景: 需要传入一个闭包，有且只有一个参数时
names2 = names.sort {$0 <= $1}
print(names2)


// 闭包捕获上下文变量，并在生命周期内存储变量值，常例： 嵌套函数种
func makeIncrementer(forIncrement amount: Int) -> () -> Int {
var runningTotal = 0
func incrementer() -> Int {
runningTotal += amount
return runningTotal
}
return incrementer
}
let increment_fn = makeIncrementer(forIncrement: 10)
print(increment_fn())
print(increment_fn())