Physics Joints - Learn SpriteBuilder for iOS Game Development - page 319

Listing 9-6 . Importing SpringBoard.h in GameScene.m
#import "GameScene.h"
#import "Trigger.h"
#import "GameMenuLayer.h"
#import "GameState.h"
#import "SpringBoard.h"
Then add the method in Listing 9-7 just below the other ccPhysicsCollisionBe-
gin methods.
Listing 9-7 . Responding to collisions between player and spring
-(BOOL)
ccPhysicsCollisionBegin:(CCPhysicsCollisionPair*)pair
player:(CCNode*)player
spring:(SpringBoard*)spring
{
[spring letGo];
return YES;
}
Now when the player collides with a physics body whose Collision type is set to
spring , it will run the method in Listing 9-7 , which in turn calls the SpringBoard 's
letGo method. Here we can safely assume that all springs are instances of the
SpringBoard class; therefore, it's safe to assume the spring parameter to be of type
SpringBoard* rather than CCNode* .
Returning YES from the method ensures the player and spring do collide rather than
passing through each other.
That's it for the spring. You can now place instances of Spring.ccb in the level. You
should add them to the chains & ropes & springs node. When you run the game and touch
a spring with the player, the spring should accelerate outward, pushing the player away.
You can alter the spring joint's damping and stiffness parameters as well as the po-
sition of the spring's world hook (by editing Anchor A ) to alter the spring force.
Breaking Joints and Motors