block

__block int i = 0;
int (^count)(void) = ^ {
i += 1;
return i;
};
NSLog(@"%d", count());    // 1
NSLog(@"%d", count());    // 2
NSLog(@"%d", count());    // 3

int q = 42;
__block int ssy = 1;
void (^block)() = ^() {
printf("1111111111111111  %d\n", q);  //42
printf("2222222222222222  %d\n", ssy);//1 2
};

block();
//输出 42  1
ssy = 2;
q = 1;

block();
//输出 42  2