block面试demo

文章写的不错额

Demo1:

inta =10;

    void(^printA)(intb);

    printA = ^(int c) {

        NSLog(@"%d, %d",a, c);

        //a = 40;

    };

    a =20;

    printA(30);

    NSLog(@"%d",a);

2019-04-07 15:55:32.326328+0800 Demo[1300:54154] 10, 30

2019-04-07 15:55:32.326726+0800 Demo[1300:54154] 20

Demo2:

__block int a = 10;

    void(^printA)(intb);

    printA = ^(int c) {

        NSLog(@"%d, %d",a, c);

        a =40;

    };

    a =20;

    printA(30);

    NSLog(@"%d",a);

2019-04-07 15:56:57.108371+0800 Demo[1309:54986] 20, 30

2019-04-07 15:56:57.108502+0800 Demo[1309:54986] 40

思考：_ _block作用