您可以通过代码或简单地在故事板上执行以下操作来解决此问题：

将UILabel的行数设置为0。将UILabel嵌入UIView中。设置UIView约束（顶部、右侧、左侧和底部），以占用UILabel应增长到的最大空间。然后将UILabel设置为UIView的顶部、右侧和左侧，并将约束设置为底部，距离>=0。

使用textRect（对于边界：limitedToNumberOfLines:）。

class TopAlignedLabel: UILabel {
  override func drawText(in rect: CGRect) {
    let textRect = super.textRect(forBounds: bounds, limitedToNumberOfLines: numberOfLines)
    super.drawText(in: textRect)
  }
}

不要大惊小怪

@interface MFTopAlignedLabel : UILabel

@end


@implementation MFTopAlignedLabel

- (void)drawTextInRect:(CGRect) rect
{
    NSAttributedString *attributedText = [[NSAttributedString alloc]     initWithString:self.text attributes:@{NSFontAttributeName:self.font}];
    rect.size.height = [attributedText boundingRectWithSize:rect.size
                                            options:NSStringDrawingUsesLineFragmentOrigin
                                            context:nil].size.height;
    if (self.numberOfLines != 0) {
        rect.size.height = MIN(rect.size.height, self.numberOfLines * self.font.lineHeight);
    }
    [super drawTextInRect:rect];
}

@end

没有混乱，没有Objective-c，没有大惊小怪，只有Swift 3:

class VerticalTopAlignLabel: UILabel {

    override func drawText(in rect:CGRect) {
        guard let labelText = text else {  return super.drawText(in: rect) }

        let attributedText = NSAttributedString(string: labelText, attributes: [NSFontAttributeName: font])
        var newRect = rect
        newRect.size.height = attributedText.boundingRect(with: rect.size, options: .usesLineFragmentOrigin, context: nil).size.height

        if numberOfLines != 0 {
            newRect.size.height = min(newRect.size.height, CGFloat(numberOfLines) * font.lineHeight)
        }

        super.drawText(in: newRect)
    }

}

雨燕4.2

class VerticalTopAlignLabel: UILabel {

    override func drawText(in rect:CGRect) {
        guard let labelText = text else {  return super.drawText(in: rect) }

        let attributedText = NSAttributedString(string: labelText, attributes: [NSAttributedString.Key.font: font])
        var newRect = rect
        newRect.size.height = attributedText.boundingRect(with: rect.size, options: .usesLineFragmentOrigin, context: nil).size.height

        if numberOfLines != 0 {
            newRect.size.height = min(newRect.size.height, CGFloat(numberOfLines) * font.lineHeight)
        }

        super.drawText(in: newRect)
    }

}

我重复了戴莱辛的建议，并添加了一个UIEdgeInset，以允许调整边距。周围环境不错。

- (id)init
{
    if (self = [super init]) {
        contentEdgeInsets = UIEdgeInsetsZero;
    }

    return self;
}

- (void)layoutSubviews
{
    CGRect localBounds = self.bounds;
    localBounds = CGRectMake(MAX(0, localBounds.origin.x + contentEdgeInsets.left), 
                             MAX(0, localBounds.origin.y + contentEdgeInsets.top), 
                             MIN(localBounds.size.width, localBounds.size.width - (contentEdgeInsets.left + contentEdgeInsets.right)), 
                             MIN(localBounds.size.height, localBounds.size.height - (contentEdgeInsets.top + contentEdgeInsets.bottom)));

    for (UIView *subview in self.subviews) {
        if ([subview isKindOfClass:[UILabel class]]) {
            UILabel *label = (UILabel*)subview;
            CGSize lineSize = [label.text sizeWithFont:label.font];
            CGSize sizeForText = [label.text sizeWithFont:label.font constrainedToSize:localBounds.size lineBreakMode:label.lineBreakMode];

            NSInteger numberOfLines = ceilf(sizeForText.height/lineSize.height);

            label.numberOfLines = numberOfLines;
            label.frame = CGRectMake(MAX(0, contentEdgeInsets.left), MAX(0, contentEdgeInsets.top), localBounds.size.width, MIN(localBounds.size.height, lineSize.height * numberOfLines)); 
        }
    }
}

我很长一段时间都在纠结这个问题，我想分享我的解决方案。

这将为您提供一个UILabel，它将自动将文本缩小到0.5个刻度，并将文本垂直居中。故事板/IB中也提供了这些选项。

[labelObject setMinimumScaleFactor:0.5];
[labelObject setBaselineAdjustment:UIBaselineAdjustmentAlignCenters];

设置新文本：myLabel.text=@“某些文本”将最大行数设置为0（自动）：myLabel.numberOfLines=0将标签的框架设置为最大大小：myLabel.frame=CGRectMake（20,20200800）调用sizeToFit以减小框架大小，使内容刚好适合：[myLabel sizeToFit]

标签框架现在刚好足够高和宽，以适合您的文本。左上角应保持不变。我只测试了左上对齐的文本。对于其他路线，您可能需要随后修改框架。

此外，我的标签启用了换行。