简单的事例看出函数和闭包的区别

简单例子 1
func add = (function () {
    var counter = 0;
    return func sun() {return counter += 1;}
})();
 
add();
add();
add();
 
// 计数器为 3

例子2
func makeIncrementor(forIncrement amount: Int) -> () -> Int {
    var runningTotal = 0
    func incrementor() -> Int {
        runningTotal += amount
        return runningTotal
    }
    return incrementor
}

let incrementByTen = makeIncrementor(forIncrement: 10)

// 返回的值为10
incrementByTen()

// 返回的值为20
incrementByTen()

// 返回的值为30
incrementByTen()

// 返回的值为40
incrementByTen()

let alsoIncrementByTen = incrementByTen

// 返回的值也为50
print(alsoIncrementByTen())

例子3
// 普通函数
func operaShow(flag: Bool) -> (int1: Int，int2: Int) -> Int {
        func a(int1: Int, int2: Int){
                return int1 + int2
        }
        func b(int1: Int, int2: Int){
                return int1 - int2
        }
        return flag ? a:b
}
// 闭包
func operaShow(flag: Bool) -> (int1: Int，int2: Int) -> Int {
        func flag?{(int1: Int, int2: Int) -> Int in
                return int1 + int2
        }:{(int1: Int, int2: Int) -> Int in
                return int1 - int2
        {
}

operaShow(flag:true)(5,4)
operaShow(flag:false)(5,4)