动画效果如下所示：

我们使用大名鼎鼎的Facebook提供的POP框架来实现这个动画效果。

自定义一个类RDNumberAnimation继承自UIView

//
//  RDNumberAnimation.h
//  POP动画
//
//  Created by 键盘上的舞者 on 10/19/16.
//  Copyright © 2016 键盘上的舞者. All rights reserved.
//

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>

@class RDNumberAnimation;

@protocol RDNumberAnimationDelegate <NSObject>

@required
- (void)RDNumberAnimation:(RDNumberAnimation *)animation currentValue:(CGFloat)currentValue;

@end

@interface RDNumberAnimation : NSObject

@property (nonatomic, weak) id<RDNumberAnimationDelegate> delegate;

@property (nonatomic, assign) CGFloat fromValue;

@property (nonatomic, assign) CGFloat toValue;

@property (nonatomic, assign) CGFloat currentValue;

@property (nonatomic, assign) NSTimeInterval duration;

@property (nonatomic, strong) CAMediaTimingFunction *timingFunction;

/**
 *  动画开始
 */
- (void)startAnimation;
/**
 *  动画结束
 */
- (void)stopAnimation;
/**
 *  保存属性
 */
- (void)saveValues;


@end

//
//  RDNumberAnimation.m
//  POP动画
//
//  Created by 键盘上的舞者 on 10/19/16.
//  Copyright © 2016 键盘上的舞者. All rights reserved.
//

#import "RDNumberAnimation.h"
#import "POP.h"

@interface RDNumberAnimation ()

@property (nonatomic, strong) POPBasicAnimation *numberAniamtion;

@end

@implementation RDNumberAnimation

- (instancetype)init {
    if (self = [super init]) {
        self.numberAniamtion = [POPBasicAnimation animation];
    }
    return self;
}

- (void)saveValues {
    self.numberAniamtion.fromValue = @(self.fromValue);
    self.numberAniamtion.toValue = @(self.toValue);
    self.numberAniamtion.duration = self.duration;
    if (self.timingFunction) {
        self.numberAniamtion.timingFunction = self.timingFunction;
    }
}

- (void)startAnimation {
    if (self.delegate && [self.delegate respondsToSelector:@selector(RDNumberAnimation:currentValue:)]) {
        __weak RDNumberAnimation *weakSelf = self;
        self.numberAniamtion.property = [POPMutableAnimatableProperty propertyWithName:@"numberAnimation" initializer:^(POPMutableAnimatableProperty *prop) {
            
            prop.writeBlock = ^(id object, const CGFloat values[]) {
                weakSelf.currentValue = values[0];
                [weakSelf.delegate RDNumberAnimation:weakSelf currentValue:values[0]];
            };
            
        }];
        
        [self pop_addAnimation:self.numberAniamtion forKey:nil];
    }
}

- (void)stopAnimation {
    [self pop_removeAllAnimations];
}

@end

我们使用POPBasicAnimation时，常会指定它的property，这里我们不指定，并自定义它的property，使用它提供的writeBlock来获取到动画运行时的数值，然后自己定义了一个delegate，然后在使用到这个VC中实现这个delegate方法，在这个delegate里面来更新UILabel的值，这样就实现了动态更新的效果，这个效果还是蛮酷的！