SKSpriteNode collision detection error - ios7

Question

I am creating a game where a ball is suppose to bounce off from platforms. I have set up physics properties for the ball and the platform(platform only attains physics property when it's below the ball). My problem is: the ball is not bouncing (I have applied impulse in didbegincontact method) when the ball makes contact with the platform, it however detects contact.
Here is my didBeginContact Code:
- (void) didBeginContact:(SKPhysicsContact *)contact {
SKSpriteNode *firstNode, *secondNode;
firstNode = (SKSpriteNode*) contact.bodyA.node;
secondNode = (SKSpriteNode*) contact.bodyB.node;
if ((contact.bodyA.categoryBitMask == ballCategory) && (contact.bodyB.categoryBitMask == solidPlatformCategory)) {
NSLog(#"Platform Hit");
CGPoint contactPoint = contact.contactPoint;
[_ball.physicsBody applyImpulse:CGVectorMake(0, 4) atPoint:contactPoint];
}
}
///// Here is the code for SKSpriteNode Ball
- (void) addBall {
_myBall = [SKSpriteNode spriteNodeWithImageNamed:#"ball.png"];
if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
_myBall.scale = 0.4;
} else {
_myBall.scale = 0.3;
}
_ball.position = CGPointMake(self.frame.size.width/2, _solidPlatform.position.y + 2.5*_ball.size.height);
_ball.zPosition = 2;
_ball.name = #"doodle";
_ball.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:_myDoodle.frame.size];
_ball.physicsBody.mass = 1.0;
_ball.physicsBody.restitution = 0.8;
_ball.physicsBody.dynamic = YES;
_ball.physicsBody.allowsRotation = NO;
_ball.physicsBody.usesPreciseCollisionDetection = YES;
_ball.physicsBody.categoryBitMask = ballCategory;
_ball.physicsBody.collisionBitMask = solidPlatformCategory;
_ball.physicsBody.contactTestBitMask = solidPlatformCategory;
//SKAction *moveUpAction = [SKAction moveByX:0.0 y:8*numberOfPlatforms duration:0.5];
[self addChild:_ball];
}
////Platform has been defined as (not a complete code):
_solidPlatform7.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:_solidPlatform7.frame.size];
_solidPlatform7.physicsBody.dynamic = NO;
_solidPlatform7.physicsBody.affectedByGravity = NO;
_solidPlatform7.physicsBody.usesPreciseCollisionDetection = YES;
_solidPlatform7.physicsBody.categoryBitMask = solidPlatformCategory;
PS: I am not getting any collusion detection if I define platform as bodyWithEdgeFromRect

Answer 1

difficult to answer without seeing some code, but I'll try:
If the ball does not bounce at all, check the restitution property. Higher values provide a higher "bounciness":
ball.physicsBody.restitution=0.8;
If you want the ball to bounce endless between bottom and ceiling you can invert the gravity after each collision:
self.physicsWorld.gravity = CGVectorMake(0, self.physicsWorld.gravity.dy * (-1));
Hope that helps. If not, please share some code.
I've tried your code. With some smaller changes it works:
- (void) addBall {
// Bottom platforms
for (int i=0; i<10; i++) {
SKSpriteNode *mySprite = [SKSpriteNode spriteNodeWithColor:[UIColor redColor] size:CGSizeMake(40, 20)];
CGPoint location = CGPointMake(i*40+60, 10);
//mySprite.size =CGSizeMake(20, 40);
mySprite.position=location;
mySprite.physicsBody=[SKPhysicsBody bodyWithRectangleOfSize:mySprite.size];
mySprite.physicsBody.dynamic=false;
mySprite.physicsBody.categoryBitMask=solidPlatformCategory;
[self addChild:mySprite];
}
_ball = [SKSpriteNode spriteNodeWithImageNamed:#"ball.png"];
if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
_ball.scale = 0.4;
} else {
_ball.scale = 0.3;
}
_ball.position = CGPointMake(self.frame.size.width/2, self.frame.size.width/2);
_ball.zPosition = 2;
_ball.name = #"doodle";
//_ball.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:_myDoodle.frame.size];
_ball.physicsBody=[SKPhysicsBody bodyWithCircleOfRadius:_ball.size.width/2];
_ball.physicsBody.mass = 1.0;
_ball.physicsBody.restitution = 1;
_ball.physicsBody.dynamic = YES;
_ball.physicsBody.allowsRotation = NO;
_ball.physicsBody.usesPreciseCollisionDetection = YES;
_ball.physicsBody.categoryBitMask = ballCategory;
_ball.physicsBody.collisionBitMask = solidPlatformCategory;
_ball.physicsBody.contactTestBitMask = solidPlatformCategory;
//SKAction *moveUpAction = [SKAction moveByX:0.0 y:8*numberOfPlatforms duration:0.5];
[self addChild:_ball];
}