Stop a sprite accurately at destination using vectors - graphics

Question

I want my sprite to move to a precise pixel location. I use the following code in the update method to move my sprite (kPlayerSpeed = 60.0f):
if (ccpDistance(self.position, requestedPosition) < kPlayerSpeed) {
[self changeState:kStateWalking];
return;
}
switch (self.characterState) {
case kStateWalkingUp:
self.position = ccp(self.position.x, self.position.y + kPlayerSpeed * deltaTime);
break;
case kStateWalkingDown:
self.position = ccp(self.position.x, self.position.y - kPlayerSpeed * deltaTime);
break;
case kStateWalkingLeft:
self.position = ccp(self.position.x - kPlayerSpeed * deltaTime, self.position.y);
break;
case kStateWalkingRight:
self.position = ccp(self.position.x + kPlayerSpeed * deltaTime, self.position.y);
break;
case kStateIdle:
break;
default:
break;
if (ccpDistance(self.position, requestedPosition) < kPlayerSpeed)
With this code the player stops near but not exactly on the spot.

Answer 1

I would do something along these lines. havent tested it though, im writing from my gfs pc.
CGPoint velocity = CGPointZero;
CGPoint delta = ccpSubstract(requestedPosition, self.position);
switch (self.characterState) {
case kStateWalkingUp:
velocity= ccp(0, kPlayerSpeed * deltaTime);
break;
case kStateWalkingDown:
velocity = ccp(0,-kPlayerSpeed * deltaTime);
break;
case kStateWalkingLeft:
velocity= ccp(-kPlayerSpeed * deltaTime, 0);
break;
case kStateWalkingRight:
velocity= ccp(kPlayerSpeed * deltaTime, 0);
break;
case kStateIdle:
break;
default:
break;
}
CGPoint signsVelocity = ccpNormalize(velocity);
CGPoint absVelocity = ccp( MIN( fabsf(velocity.x), fabsf(delta.x)) , MIN(fabsf(velocity.y), fabsf(velocity.x) );
self.position = ccpAdd(self.position, ccpMult(absVelocity, signsVelocity) );

Answer 2

Andres, thanks for the reply.
I couldn't quite get your code to work, so using your lead I did a bit more research and came up with this...
float step = kPlayerSpeed * deltaTime;
float dist = ccpDistance(self.position, requestedPosition);
if (dist <= step) {
self.position = requestedPosition;
} else {
CGPoint vectorBetweenAB = ccpSub(self.position, requestedPosition);
CGPoint normVectorBetweenPositionAndEnd = ccpNormalize(vectorBetweenAB);
CGPoint movementVectorForThisFrame = ccpMult(normVectorBetweenPositionAndEnd, step);
if (self.position.x > movementVectorForThisFrame.x) {
movementVectorForThisFrame.x = -movementVectorForThisFrame.x;
}
if (self.position.y > movementVectorForThisFrame.y) {
movementVectorForThisFrame.y = -movementVectorForThisFrame.y;
}
self.position = ccpAdd(self.position, movementVectorForThisFrame);
}
Is there a better way to do it than this?
Thanks