Physics Joints - Learn SpriteBuilder for iOS Game Development - page 317

The anchor and distance properties have been entered as they were in SpriteBuilder. That,
too, is a bit unfortunate because technically the _lockJoint instance still has all these
properties internally. However, you'd have to go through a private Objective-C API (a
private property named constraint ) to gain access to another private Chip-
munkConstraint class. In this case, the anchor and distance properties are unlikely to
change, so you can just enter them in code.
The newly created joint is assigned directly to _lockJoint , replacing the previous one.
Since the previous lock joint has no strong reference holding on to it, ARC will automat-
ically release its memory. So you really just keep the most recently created _lockJoint
in memory. And once the SpringBoard instance deallocates, the remaining _lock-
Joint instance will also deallocate.
The CCPhysicsJoint class allows you to create the same joints in code as the ones
you can edit in SpriteBuilder (pivot, spring, and distance). However, variations exist that
you can achieve only with SpriteBuilder. For instance, you can't create a pivot joint with
both spring and limit enabled through the CCPhysicsJoint interface. See Listing 9-5
for a reference of available CCPhysicsJoint initializers.
Listing 9-5 . Creating CCPhysicsJoint instances
// Creating a Spring Joint
+(CCPhysicsJoint*)connectedSpringJointWithBodyA:(CCPhysicsBody*)bodyA
bodyB:(CCPhysicsBody*)bodyB
anchorA:(CGPoint)anchorA
anchorB:(CGPoint)anchorB
restLength:(CGFloat)restLength
stiffness:(CGFloat)stiffness
damping:(CGFloat)damping;
// Creating a Distance Joint
+(CCPhysicsJoint*)connectedDistanceJointWithBodyA:(CCPhysicsBody*)bodyA
bodyB:(CCPhysicsBody*)bodyB
anchorA:(CGPoint)anchorA
anchorB:(CGPoint)anchorB;
+(CCPhysicsJoint*)connectedDistanceJointWithBodyA:(CCPhysicsBody*)bodyA
bodyB:(CCPhysicsBody*)bodyB
anchorA:(CGPoint)anchorA
anchorB:(CGPoint)anchorB