destroying a weldjoint when a sprite reaches a specific position - ios

Question

I have created a weldJoint between two sprites in my code (see update method below) and I also created a method that returns the exact position of a sprite when a mouseJoint is released. I want to compare the current position of the sprite to the spritePositionRelease value and destroy the weldJoint if the y values are the same and x values are different. Please help.
spritePositionRelease:
- (CGPoint)spritePositionRelease {
for(b2Body *b = mouseJoint->GetBodyB(); b; b=b->GetNext()) {
if (b->GetUserData() != NULL)
{
CCSprite *mySprite = (CCSprite*)b->GetUserData();
if (mySprite.tag == 1) {
mySprite.position = CGPointMake( b->GetPosition().x * PTM_RATIO, b->GetPosition().y * PTM_RATIO);
CGPoint spritePosition = mySprite.position;
CCLOG(#"the sprite position is x:%0.2f , y:%0.2f", spritePosition.x, spritePosition.y);
return spritePosition;
}
}
}
}
ccTouchesEnded:
- (void)ccTouchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
if (mouseJoint)
{
[self spritePositionRelease];
world->DestroyJoint(mouseJoint);
mouseJoint = NULL;
}
}
update:
-(void) update: (ccTime) dt
{
//It is recommended that a fixed time step is used with Box2D for stability
//of the simulation, however, we are using a variable time step here.
//You need to make an informed choice, the following URL is useful
//http://gafferongames.com/game-physics/fix-your-timestep/
int32 velocityIterations = 8;
int32 positionIterations = 1;
// Instruct the world to perform a single step of simulation. It is
// generally best to keep the time step and iterations fixed.
world->Step(dt, velocityIterations, positionIterations);
// using the iterator pos over the set
std::set<BodyPair *>::iterator pos;
for(pos = bodiesForJoints.begin(); pos != bodiesForJoints.end(); ++pos)
{
b2WeldJoint *weldJoint;
b2WeldJointDef weldJointDef;
BodyPair *bodyPair = *pos;
b2Body *bodyA = bodyPair->bodyA;
b2Body *bodyB = bodyPair->bodyB;
weldJointDef.Initialize(bodyA,
bodyB,
bodyA->GetWorldCenter());
weldJointDef.collideConnected = false;
weldJoint = (b2WeldJoint*) world->CreateJoint(&weldJointDef);
// Free the structure we allocated earlier.
free(bodyPair);
// Remove the entry from the set.
bodiesForJoints.erase(pos);
}
}

Answer 1

Are you sure that mouseJoint->GetBodyB() will always return the right body? Maybe you should check mouseJoint->GetBodyA() to?
Anyway your check would be quite simple:
- (void)ccTouchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
if (mouseJoint)
{
CGPoint releasePoint = [self spritePositionRelease];
CGPoint touchPoint = [[touches anyObject] locationInView:[[touches anyObject] view]];
if((releasePoint.y==touchPoint.y) &&(releasePoint.x!=touchPoint.x))
{
//Destroy weld joint
}
world->DestroyJoint(mouseJoint);
mouseJoint = NULL;
}
}