ruby>>
inline CAAnimation*
BounceAnimationElement( CGPoint pFrom, CGPoint pTo, double pBeginTime, double pDuration, CAMediaTimingFunction* pMTF )
{ CABasicAnimation* v = [ CABasicAnimation animationWithKeyPath:@"position" ];
v.fromValue = [ NSValue valueWithCGPoint:pFrom ];
v.toValue = [ NSValue valueWithCGPoint:pTo ];
v.beginTime = pBeginTime;
v.duration = pDuration;
v.timingFunction = pMTF;
return v;
}

inline CAAnimation*
BounceAnimation( CALayer* pL, CGPoint pDest, double pInitialDuration = 1, double pK = .3, size_t pRepeat = 10 )
{ CAMediaTimingFunction* wMTF_D = [ CAMediaTimingFunction functionWithControlPoints:1./3. :0 :2./3. :1./3. ];
CAMediaTimingFunction* wMTF_U = [ CAMediaTimingFunction functionWithControlPoints:1./3. :2./3. :2./3. :1 ];

CGPoint wOrigin = pL.position;

NSMutableArray* wAnimationArray = NSMutableArray.array;
[ wAnimationArray addObject:BounceAnimationElement( pL.position, pDest, 0, pInitialDuration, wMTF_D ) ];

double	wBeginTime = pInitialDuration;

double	wK = 1;
while ( pRepeat-- )
{	wK *= pK;
	CGPoint wPoint = CGPointMake
	(	wOrigin.x * wK + pDest.x * ( 1 - wK )
	,	wOrigin.y * wK + pDest.y * ( 1 - wK )
	);
	double wDuration = pInitialDuration * wK * ( 1 / sqrt( wK ) );
	[ wAnimationArray addObject:BounceAnimationElement( pDest, wPoint, wBeginTime, wDuration, wMTF_U ) ];
	wBeginTime += wDuration;
	[ wAnimationArray addObject:BounceAnimationElement( wPoint, pDest, wBeginTime, wDuration, wMTF_D ) ];
	wBeginTime += wDuration;
}

pL.position = pDest;

CAAnimationGroup* v = CAAnimationGroup.animation;
v.duration = wBeginTime;
v.animations = wAnimationArray;

return v;

}

• (IBAction)
  Group
  { [ mL addAnimation:BounceAnimation( mL, CGPointMake( 160, 240 ) ) forKey:nil ];

}

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