你的方向是对的。你所需要做的就是:

myUILabel.numberOfLines = 0;
myUILabel.text = @"Enter large amount of text here";
[myUILabel sizeToFit];

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);
}

iOS7之前和iOS7上面的解决方案

//
//  UILabel+DynamicHeight.m
//  For StackOverFlow
//
//  Created by Vijay on 24/02/14.
//  Copyright (c) 2014 http://Vijay-Apple-Dev.blogspot.com. All rights reserved.
//

#import <UIKit/UIKit.h>

#define SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(v)  ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] != NSOrderedAscending)

#define SYSTEM_VERSION_LESS_THAN(v)                 ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] == NSOrderedAscending)

#define iOS7_0 @"7.0"

@interface UILabel (DynamicHeight)

/*====================================================================*/

/* Calculate the size,bounds,frame of the Multi line Label */

/*====================================================================*/
/**
 *  Returns the size of the Label
 *
 *  @param aLabel To be used to calculte the height
 *
 *  @return size of the Label
 */

-(CGSize)sizeOfMultiLineLabel;

@end


//
//  UILabel+DynamicHeight.m
//  For StackOverFlow
//
//  Created by Vijay on 24/02/14.
//  Copyright (c) 2014 http://Vijay-Apple-Dev.blogspot.com. All rights reserved.
//

#import "UILabel+DynamicHeight.h"

@implementation UILabel (DynamicHeight)
/*====================================================================*/

/* Calculate the size,bounds,frame of the Multi line Label */

/*====================================================================*/
/**
 *  Returns the size of the Label
 *
 *  @param aLabel To be used to calculte the height
 *
 *  @return size of the Label
 */
-(CGSize)sizeOfMultiLineLabel{

    NSAssert(self, @"UILabel was nil");

    //Label text
    NSString *aLabelTextString = [self text];

    //Label font
    UIFont *aLabelFont = [self font];

    //Width of the Label
    CGFloat aLabelSizeWidth = self.frame.size.width;


    if (SYSTEM_VERSION_LESS_THAN(iOS7_0)) {
        //version < 7.0

        return [aLabelTextString sizeWithFont:aLabelFont
                            constrainedToSize:CGSizeMake(aLabelSizeWidth, MAXFLOAT)
                                lineBreakMode:NSLineBreakByWordWrapping];
    }
    else if (SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(iOS7_0)) {
        //version >= 7.0

        //Return the calculated size of the Label
        return [aLabelTextString boundingRectWithSize:CGSizeMake(aLabelSizeWidth, MAXFLOAT)
                                              options:NSStringDrawingUsesLineFragmentOrigin
                                           attributes:@{
                                                        NSFontAttributeName : aLabelFont
                                                        }
                                              context:nil].size;

    }

    return [self bounds].size;

}

@end

myLabel.text = "your very long text"
myLabel.numberOfLines = 0
myLabel.lineBreakMode = NSLineBreakMode.ByWordWrapping

请在故事板中为可用性设置约束，包括左上右下

你的方向是对的。你所需要做的就是:

myUILabel.numberOfLines = 0;
myUILabel.text = @"Enter large amount of text here";
[myUILabel sizeToFit];

我的代码:

UILabel *label      = [[UILabel alloc] init];
label.numberOfLines = 0;
label.lineBreakMode = NSLineBreakByWordWrapping;
label.text          = text;
label.textAlignment = NSTextAlignmentCenter;
label.font          = [UIFont fontWithName:_bodyTextFontFamily size:_bodyFontSize];

CGSize size = [label sizeThatFits:CGSizeMake(width, MAXFLOAT)];


float height        = size.height;
label.frame         = CGRectMake(x, y, width, height);