block 전송값 (2)

이전 Block 코드 블록의 기초 사용 추가 (1)
ViewController

- (IBAction)gotoNextVC:(UIButton *)sender
{
    SecondVC *vc = [[SecondVC alloc]init];    
    //                block ，   block         ，                block          。
    vc.changeColorBlock = ^(UIColor *color)
    {
        self.view.backgroundColor = color;
    };
    [self.navigationController pushViewController:vc animated:YES];
}

//block property    copy
@property (nonatomic,copy)void (^changeColorBlock)(UIColor *);

- (IBAction)changeColor:(UIButton *)sender
{
    UIColor *color = nil;
    switch (sender.tag)
    {
        case 1:
            color = [UIColor redColor];
            break;
        case 2:
            color = [UIColor greenColor];
            break;
        case 3:
            color = [UIColor blueColor];
            break;
        default:
            break;
    }
    
    //  block
    if (_changeColorBlock)
    {
        //  block     ，    block    ，         block    。
        _changeColorBlock(color);
    }
    [self.navigationController popViewControllerAnimated:YES];
}