FadingLabel.h

//
//  FadingLabel.h
//  TextCrossFade
//
//  Created by Paul Wilkinson on 30/09/2015.
//  Copyright © 2015 Paul Wilkinson. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface FadingLabel : UILabel

-(void) embiggen;
-(void) debiggen;

@end

FadingLabel.m

//
//  FadingLabel.m
//  TextCrossFade
//
//  Created by Paul Wilkinson on 30/09/2015.
//  Copyright © 2015 Paul Wilkinson. All rights reserved.
//

#import "FadingLabel.h"

@implementation FadingLabel

/*
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
    // Drawing code
}
*/

-(void) embiggen {

    CGSize newSize = [self.text boundingRectWithSize:CGSizeMake(self.frame.size.width, MAXFLOAT)
                                                   options:NSStringDrawingUsesLineFragmentOrigin
                                                attributes:@{
                                                             NSFontAttributeName : self.font
                                                             }
                                                   context:nil].size;
    
    CGRect newRect = CGRectMake(self.frame.origin.x, self.frame.origin.y, self.frame.size.width, newSize.height);
            self.frame = newRect;
    [UIView transitionWithView:self duration:0.3 options:UIViewAnimationOptionTransitionCrossDissolve animations:^{
        self.numberOfLines = 0;

    } completion:^(BOOL finished) {
        
     //   self.backgroundColor = [UIColor orangeColor];
    }];
}

-(void) debiggen {
    
    CGSize newSize = [@" " boundingRectWithSize:CGSizeMake(self.frame.size.width, MAXFLOAT)
                                             options:NSStringDrawingUsesLineFragmentOrigin
                                          attributes:@{
                                                       NSFontAttributeName : self.font
                                                       }
                                             context:nil].size;
    
    CGRect newRect = CGRectMake(self.frame.origin.x, self.frame.origin.y, self.frame.size.width, newSize.height);
            self.frame = newRect;
    [UIView transitionWithView:self duration:0.3 options:UIViewAnimationOptionTransitionCrossDissolve animations:^{
        self.numberOfLines = 1;

    } completion:^(BOOL finished) {
        
      //  self.backgroundColor = [UIColor greenColor];
    }];
}

@end