UILabel怎么做到顶端对齐

一个UILabel，如果内容很短的话就会垂直居中，但是我希望他顶端对齐，改怎么做？

UILabel *label = [[UILabel alloc] initWithFrame:self.view.bounds];
label.text = @"各种居中";
label.textAlignment = UITextAlignmentCenter;
[self.view addSubview:label];

---

label.numberOfLines = 0;
[label sizeToFit];

---

@implementation UILabel (VerticalUpAlignment)

- (void)verticalUpAlignmentWithText:(NSString *)text maxHeight:(CGFloat)maxHeight
{
    CGRect frame = self.frame;
    CGSize size = [text sizeWithFont:self.font constrainedToSize:CGSizeMake(frame.size.width, maxHeight)];
    frame.size = CGSizeMake(frame.size.width, size.height);
    self.frame = frame;
    self.text = text;
}

@end