using block and callback

gistfile1.m

//block declare: 
typedef int (^startBlock)(int a, int b);
typedef int (^endBlock)();

- (void) runBlock:(startBlock)_startBlock end:(endBlock)_endBlock{
    int a = _startBlock(1,2);
    int b = _endBlock();
    NSLog(@"start block result : %d", a);
    NSLog(@"end block result : %d", b);
}

//run block: 
[self runBlock:^int(int a, int b) {
        NSLog(@"args from run-block : %d, %d ", a, b);
        return 1;
} end:^int{
        return 2;
}];