Swift与Objective－C中的闭包

Swift Code:

    func makeIncrementor(forIncrement amount: Int) -> (() -> Int,() -> Int) {

        var runningTotal = 0

        func incrementor() -> Int {

            runningTotal += amount

            return runningTotal

        }

        func decrementor()->Int{

            runningTotal -= amount

            return runningTotal

        }

        runningTotal += 1000;

        return (incrementor,decrementor)

    }

    let counter = makeIncrementor(forIncrement: 1);

    let a1 = counter.0();

    assert(a1==1001, "a1")

    let a2 = counter.0();

    assert(a2==1002, "a2")

    let a3 = counter.0();

    assert(a3==1003, "a3")

    let c1 = counter.1();

    assert(c1==1002, "c1")

 Objective-C Code:

        __block int runningTotal = 0;
        
        int (^incrementor)() = ^(){
            return ++runningTotal;
        };
        
        int (^decrementor)() = ^(){
            return --runningTotal;
        };
        runningTotal=1000;
        int a1 = incrementor();
        int a2 = incrementor();
        int a3 = incrementor();
        int c1 = decrementor();