iOS在固定的label上动态显示所有文字

UILabel* contentLabel = [[UILabel alloc] init];
[contentLabel sizeToFit];
contentLabel.backgroundColor = [UIColor clearColor]; _contentLabel = contentLabel; [self addSubview:self.contentLabel];

CAShapeLayer* maskLayer = [CAShapeLayer layer];
maskLayer.path = [UIBezierPath bezierPathWithRect:self.bounds].CGPath;
self.layer.mask = maskLayer;

CAKeyframeAnimation* keyFrame = [CAKeyframeAnimation animation];
keyFrame.keyPath = @"transform.translation.x";
keyFrame.values = @[@(0), @(-space), @(0)];
keyFrame.repeatCount = NSIntegerMax;
keyFrame.duration = self.speed * self.contentLabel.text.length;
keyFrame.timingFunctions = @[[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut], [CAMediaTimingFunction functionWithControlPoints:0 :0 :0.5 :0.5]];
keyFrame.delegate = self;
[self.contentLabel.layer addAnimation:keyFrame forKey:nil];

// 创建
CFDynamicLabel* testLabel = [[CFDynamicLabel alloc] initWithFrame:CGRectMake(100, 300, 180, 21)];
// 设置滚动速度
testLabel.speed = 0.6;
[self.view addSubview:testLabel];
// 设置基本属性
testLabel.text = @"我不想说再见,不说再见,越长大越孤单";
testLabel.textColor = [UIColor yellowColor];
testLabel.font = [UIFont systemFontOfSize:23];
testLabel.backgroundColor = [UIColor grayColor];