Overview

Delegate type called when two physics bodies collide.

The final two parameter names (typeA/typeB) should be replaced with names used with CCPhysicsBody.collisionType or CCPhysicsShape.collisionType. If both final parameter names are “default” then the collision method is called when a more specific method isn’t found.

Wildcard Collisions:

“wildcard” can be used as the final parameter name to mean “collides with anything”. When using wildcard methods, it’s possible for up to three methods to be called (ex: bullet/monster, bullet/wildcard, monster/wildcard). The most specific method (bullet/monster) will be called first, and then the wildcard handlers will be called in a somewhat random order. Begin and PreSolve methods return a boolean. If multiple methods are called, their return values are combined with a logical AND.

Collision Sequence:

On the first fixed time step (not necessarily frame) that two physics shapes collide for the first time, a ccPhysicsCollisionBegin method will be called. As long as those objects stay in contact, a ccPhysicsCollisionPreSolve and ccPhysicsCollisionPostSolve method will be called before and after the physics solver runs. The pre-solve method gives you a chance to modify the outcome of the collision, and the post-solve method lets you find out what the outcome was. This means you cannot use the outcome of the collision to modify itself. (ex: discard or undo a collision only if it will cause enough damage) Finally, when two physics objects stop touching for the very first fixed time step, the ccPhysicsCollisionSeparate method is called.

CCPhysicsShape vs. CCPhysicsBody:

Though CCPhysics concentrates mostly on physics bodies, the underlying physics engine (Chipmunk2D) operates collision callbacks on the level of individual shapes. CCPhysicsBody objects can have multiple shapes such as polyline bodies or those created with [CCPhysicsBody bodyWithShapes:]. In those cases, its possible to have have multiple active collisions between two CCPhysicsBody objects. This is something to keep in mind.