由于sizeWithFont已弃用，我使用这个代替。

这个得到标签特定属性。

-(CGFloat)heightForLabel:(UILabel *)label withText:(NSString *)text{

    NSAttributedString *attributedText = [[NSAttributedString alloc] initWithString:text attributes:@{NSFontAttributeName:label.font}];
    CGRect rect = [attributedText boundingRectWithSize:(CGSize){label.frame.size.width, CGFLOAT_MAX}
                                           options:NSStringDrawingUsesLineFragmentOrigin
                                           context:nil];

    return ceil(rect.size.height);
}

再加上上述答案:

这可以通过故事板轻松实现。

为UILabel设置约束。(在我的情况下，我做了顶部，左边和固定宽度) 在“属性检查器”中将“行数”设置为0 在“属性检查器”中将换行符设置为“WordWrap”。

以下是分类版本:

UILabel + AutoSize.h #进口

@interface UILabel (AutoSize)

- (void) autosizeForWidth: (int) width;

@end

UILabel + AutoSize。m

#import "UILabel+AutoSize.h"

@implementation UILabel (AutoSize)

- (void) autosizeForWidth: (int) width {
    self.lineBreakMode = UILineBreakModeWordWrap;
    self.numberOfLines = 0;
    CGSize maximumLabelSize = CGSizeMake(width, FLT_MAX);
    CGSize expectedLabelSize = [self.text sizeWithFont:self.font constrainedToSize:maximumLabelSize lineBreakMode:self.lineBreakMode];
    CGRect newFrame = self.frame;
    newFrame.size.height = expectedLabelSize.height;
    self.frame = newFrame;
}

@end

你也可以把它作为一种方法。@Pyjamasam是非常正确的，所以我只是在创建它的方法。它可能对其他人有帮助

-(CGRect)setDynamicHeightForLabel:(UILabel*)_lbl andMaxWidth:(float)_width{
    CGSize maximumLabelSize = CGSizeMake(_width, FLT_MAX);

    CGSize expectedLabelSize = [_lbl.text sizeWithFont:_lbl.font constrainedToSize:maximumLabelSize lineBreakMode:_lbl.lineBreakMode];

    //adjust the label the the new height.
    CGRect newFrame = _lbl.frame;
    newFrame.size.height = expectedLabelSize.height;
    return newFrame;
}

就像这样

label.frame = [self setDynamicHeightForLabel:label andMaxWidth:300.0];

要在Swift3中做到这一点，以下是代码:

 let labelSizeWithFixedWith = CGSize(width: 300, height: CGFloat.greatestFiniteMagnitude)
            let exactLabelsize = self.label.sizeThatFits(labelSizeWithFixedWith)
            self.label.frame = CGRect(origin: CGPoint(x: 20, y: 20), size: exactLabelsize)

NSString *str = @"Please enter your text......";
CGSize lblSize = [str sizeWithFont:[UIFont systemFontOfSize:15] constrainedToSize: CGSizeMake(200.0f, 600.0f) lineBreakMode: NSLineBreakByWordWrapping];

UILabel *label = [[UILabel alloc]init];
label.frame = CGRectMake(60, 20, 200, lblSize.height);
label.numberOfLines = 0;
label.lineBreakMode = NSLineBreakByWordWrapping;
label.font = [UIFont systemFontOfSize:15];
label.text = str;
label.backgroundColor = [UIColor clearColor];
[label sizeToFit];
[self.view addSubview:label];