WZTransitionLabel is a subclass of UILabel that provide custom transition when switching label's text.
You can install it by adding pod 'WZTransitionLabel' to your pod spec, or just simply drag WZTransitionLabel.h adn WZTransitionLabel.m to your project.
WZTransitionLabel *label = [[WZTransitionLabel alloc] initWithFrame:CGRectMake(0, 0, 300, 200)];
label.attributedText = [[NSAttributedString alloc] initWithString:@"test string" attributes:@{NSForegroundColorAttributeName: [UIColor blackColor]}];
NSAttributedString *toString = [[NSAttributedString alloc] initWithString:@"another string" attributes@{NSForegroundColorAttributeName:[UIColor redColor]}];
[label transiteToAttributedString:toString animated:YES duration:1.5];