Facebook Pop Animating CGPath - CoreAnimation + Pop

gistfile1.m

CGFloat height = 100.f;
    
    
    UIBezierPath *straightPath = [UIBezierPath bezierPath];
    [straightPath moveToPoint:CGPointMake(0, 0)];
    [straightPath addCurveToPoint:CGPointMake(0, height) controlPoint1:CGPointMake(0, height * 0.5) controlPoint2:CGPointMake(0, height * 0.5)];
    
    
    UIBezierPath *bendiPath = [UIBezierPath bezierPath];
    [bendiPath moveToPoint:CGPointMake(0, 0)];
    [bendiPath addCurveToPoint:CGPointMake(0, height) controlPoint1:CGPointMake(40, height * 0.5) controlPoint2:CGPointMake(40, height * 0.5)];
    
    UIBezierPath *bendiPath2 = [UIBezierPath bezierPath];
    [bendiPath2 moveToPoint:CGPointMake(0, 0)];
    [bendiPath2 addCurveToPoint:CGPointMake(0, height) controlPoint1:CGPointMake(-40, height * 0.5) controlPoint2:CGPointMake(-40, height * 0.5)];
    
    
    shape = [CAShapeLayer layer];
    shape.path = straightPath.CGPath;
    shape.strokeColor = [UIColor blackColor].CGColor;
    shape.lineWidth = 10.f;
    shape.fillColor = nil;
    shape.position = self.view.center;
    [self.view.layer addSublayer:shape];
    
  
    CAKeyframeAnimation *keyFrame = [CAKeyframeAnimation animationWithKeyPath:@"path"];
    keyFrame.values = @[(__bridge id)(straightPath.CGPath),(__bridge id)(bendiPath.CGPath),(__bridge id)(straightPath.CGPath),(__bridge id)(bendiPath2.CGPath),(__bridge id)(straightPath.CGPath)];
    keyFrame.duration = 100.0f;
    keyFrame.additive = YES;
    keyFrame.removedOnCompletion = NO;
    keyFrame.fillMode = kCAFillModeForwards;
    
    [shape addAnimation:keyFrame forKey:nil];
    shape.speed = 0.0;
    
        //    return;
        self.pop = [POPAnimatableProperty propertyWithName:@"timeOffset" initializer:^(POPMutableAnimatableProperty *prop) {
            // read value
            prop.readBlock = ^(CAShapeLayer *obj, CGFloat values[]) {
                values[0] = obj.timeOffset;
            };
            // write value
            prop.writeBlock = ^(CAShapeLayer *obj, const CGFloat values[]) {
                    obj.timeOffset = values[0];
            };
            // dynamics threshold
            prop.threshold = 0.1;
        }];

        self.anim = [POPSpringAnimation animation];
        _anim.fromValue = @(0.0);
        _anim.toValue =  @(100.f);
        _anim.springBounciness = 20.1;
        _anim.springSpeed = 20.4;
        _anim.dynamicsTension = 200;
        _anim.dynamicsFriction = 100.f;
        _anim.dynamicsMass = 1.f;
        _anim.property = self.pop;
        [shape pop_addAnimation:_anim forKey:nil];

better add

shape.timeOffset = 0;

when initialize