你应该试试这个:

-(CGFloat)dynamicLblHeight:(UILabel *)lbl
{
    CGFloat lblWidth = lbl.frame.size.width;
    CGRect lblTextSize = [lbl.text boundingRectWithSize:CGSizeMake(lblWidth, MAXFLOAT)
                                               options:NSStringDrawingUsesLineFragmentOrigin
                                            attributes:@{NSFontAttributeName:lbl.font}
                                               context:nil];
    return lblTextSize.size.height;
}

斯威夫特4:

label.lineBreakMode = .byWordWrapping

label.numberOfLines = 0

label.translatesAutoresizingMaskIntoConstraints = false

label.preferredMaxLayoutWidth = superview.bounds.size.width - 10 

这段代码根据文本返回大小和高度

+ (CGFloat)findHeightForText:(NSString *)text havingWidth:(CGFloat)widthValue andFont:(UIFont *)font
 {
    CGFloat result = font.pointSize+4;
    if (text) 
{
        CGSize size;

        CGRect frame = [text boundingRectWithSize:CGSizeMake(widthValue, 999)
                                          options:NSStringDrawingUsesLineFragmentOrigin
                                       attributes:@{NSFontAttributeName:font}
                                          context:nil];
        size = CGSizeMake(frame.size.width, frame.size.height+1);
        result = MAX(size.height, result); //At least one row
    }
    return result;
}

设置换行模式为换行，行数为0:

// Swift
textLabel.lineBreakMode = .byWordWrapping
textLabel.numberOfLines = 0

// Objective-C
textLabel.lineBreakMode = NSLineBreakByWordWrapping;
textLabel.numberOfLines = 0;

// C# (Xamarin.iOS)
textLabel.LineBreakMode = UILineBreakMode.WordWrap;
textLabel.Lines = 0;  

恢复旧答案(供参考和开发者愿意支持iOS 6.0以下):

textLabel.lineBreakMode = UILineBreakModeWordWrap;
textLabel.numberOfLines = 0;

另一方面:两个enum值都为0。

斯威夫特3 设置行数为零的动态文本信息，这将是有用的变化文本。

var label = UILabel()
let stringValue = "A label\nwith\nmultiline text."
label.text = stringValue
label.numberOfLines = 0
label.lineBreakMode = .byTruncatingTail // or .byWrappingWord
label.minimumScaleFactor = 0.8 . // It is not required but nice to have a minimum scale factor to fit text into label frame

在IB中，将行数设置为0(允许无限行)

当使用IB在文本框中输入时，使用“alt-return”插入一个返回值并转到下一行(或者您可以复制已经被行隔开的文本)。