对于Swift 3。。。

@IBDesignable class TopAlignedLabel: UILabel {
    override func drawText(in rect: CGRect) {
        if let stringText = text {
            let stringTextAsNSString = stringText as NSString
            let labelStringSize = stringTextAsNSString.boundingRect(with: CGSize(width: self.frame.width,height: CGFloat.greatestFiniteMagnitude),
                                                                            options: NSStringDrawingOptions.usesLineFragmentOrigin,
                                                                            attributes: [NSFontAttributeName: font],
                                                                            context: nil).size
            super.drawText(in: CGRect(x:0,y: 0,width: self.frame.width, height:ceil(labelStringSize.height)))
        } else {
            super.drawText(in: rect)
        }
    }
    override func prepareForInterfaceBuilder() {
        super.prepareForInterfaceBuilder()
        layer.borderWidth = 1
        layer.borderColor = UIColor.black.cgColor
    }
}

我接受了这里的建议，并创建了一个可以包装UILabel的视图，它将调整大小并设置行数，使其顶部对齐。只需将UILabel作为子视图：

@interface TopAlignedLabelContainer : UIView
{
}

@end

@implementation TopAlignedLabelContainer

- (void)layoutSubviews
{
    CGRect bounds = self.bounds;

    for (UILabel *label in [self subviews])
    {
        if ([label isKindOfClass:[UILabel class]])
        {
            CGSize fontSize = [label.text sizeWithFont:label.font];

            CGSize textSize = [label.text sizeWithFont:label.font
                                     constrainedToSize:bounds.size
                                         lineBreakMode:label.lineBreakMode];

            label.numberOfLines = textSize.height / fontSize.height;

            label.frame = CGRectMake(0, 0, textSize.width,
                 fontSize.height * label.numberOfLines);
        }
    }
}

@end

创建新类

标签顶部对齐

.h文件

#import <UIKit/UIKit.h>


@interface KwLabelTopAlign : UILabel {

}

@end

.m文件

#import "KwLabelTopAlign.h"


@implementation KwLabelTopAlign

- (void)drawTextInRect:(CGRect)rect {
    int lineHeight = [@"IglL" sizeWithFont:self.font constrainedToSize:CGSizeMake(rect.size.width, 9999.0f)].height;
    if(rect.size.height >= lineHeight) {
        int textHeight = [self.text sizeWithFont:self.font constrainedToSize:CGSizeMake(rect.size.width, rect.size.height)].height;
        int yMax = textHeight;
        if (self.numberOfLines > 0) {
            yMax = MIN(lineHeight*self.numberOfLines, yMax);    
        }

        [super drawTextInRect:CGRectMake(rect.origin.x, rect.origin.y, rect.size.width, yMax)];
    }
}

@end

Edit

下面是一个更简单的实现，它也做到了这一点：

#import "KwLabelTopAlign.h"

@implementation KwLabelTopAlign

- (void)drawTextInRect:(CGRect)rect
{
    CGFloat height = [self.text sizeWithFont:self.font
                            constrainedToSize:rect.size
                                lineBreakMode:self.lineBreakMode].height;
    if (self.numberOfLines != 0) {
        height = MIN(height, self.font.lineHeight * self.numberOfLines);
    }
    rect.size.height = MIN(rect.size.height, height);
    [super drawTextInRect:rect];
}

@end

使用故事板最简单的方法：

在StackView中嵌入标签，并在属性检查器中设置StackView的以下两个属性：

1-轴到水平，

2-与顶部对齐

在发布的所有其他解决方案的基础上，我创建了一个简单的小UILabel子类，在设置其对齐属性时将为您处理垂直对齐。这还将在方向更改时更新标签，将高度约束到文本，并将标签的宽度保持在其原始大小。

.h

@interface VAlignLabel : UILabel
@property (nonatomic, assign) WBZVerticalAlignment alignment;
@end


.m

 -(void)setAlignment:(WBZVerticalAlignment)alignment{

    _alignment = alignment;

    CGSize s = [self.text sizeWithFont:self.font constrainedToSize:CGSizeMake(self.frame.size.width, 9999) lineBreakMode:NSLineBreakByWordWrapping];

    switch (_alignment)
    {
        case wbzLabelAlignmentVerticallyTop:
            self.frame = CGRectMake(self.frame.origin.x, self.frame.origin.y, self.frame.size.width, s.height);
            break;
        case wbzLabelAlignmentVerticallyMiddle:
            self.frame = CGRectMake(self.frame.origin.x, self.frame.origin.y + (self.frame.size.height - s.height)/2, self.frame.size.width, s.height);
            break;
        case wbzLabelAlignmentVerticallyBottom:
            self.frame = CGRectMake(self.frame.origin.x, self.frame.origin.y + (self.frame.size.height - s.height), self.frame.size.width, s.height);
            break;
        default:
            break;
    }
}

-(void)layoutSubviews{
    [self setAlignment:self.alignment];
}

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)
    }

}