开关语句和If语句

Question

为什么开关大小写不需要多行，如果做得很好

if(indexPath.row == 1){
            UIViewController *viewController = [UIViewController new];
            viewController.view.backgroundColor = [UIColor whiteColor];
            viewController.title = _titlesArray[indexPath.row];
            [self.navigationController pushViewController:viewControlleranimated:YES];
}

无法在switch语句中使用的相同代码

            switch (indexPath.row) {
                case 0:
                    UIViewController *viewController = [UIViewController new];
                    viewController.view.backgroundColor = [UIColor whiteColor];
                    viewController.title = _titlesArray[indexPath.row];
                     [self.navigationController pushViewController:viewControlleranimated:YES];
    break;
                    case 1:
                    break;

                    default
                     break:
}

在开关语句中，它给出了一个错误..。我强制使用if else语句来安装开关箱。有谁能建议我如何使用开关案例的状态。

Answer 1

只要没有变量定义，开关将占用多行。任何新的定义都需要附上。因此，这两者都是有效的：

case 0:
{
    UIViewController *viewController = [UIViewController new];
    viewController.view.backgroundColor = [UIColor whiteColor];
    viewController.title = _titlesArray[indexPath.row];
    [self.navigationController pushViewController:viewControlleranimated:YES];
break;
}

和

UIViewController *viewController;

...

case 0:
    viewController = [UIViewController new];
    viewController.view.backgroundColor = [UIColor whiteColor];
    viewController.title = _titlesArray[indexPath.row];
    [self.navigationController pushViewController:viewControlleranimated:YES];
break;