title: Why is collision detection no longer working in cocos2d v3?
body: <p>In old project i create collisions like in this question:  <a href="https://stackoverflow.com/questions/23555715/why-collision-not-working-cocos2d-v3/23560185#23560185">why collision not working , cocos2d v3?</a> .
  It ran ok, however when I created a new project something was wrong.
  I don't know what I did differently this time. Please help me.</p>
  
  <pre><code>-(void)addAIAction:(int)i{
      if (!arrAI) {
          arrAI = [[NSMutableArray alloc]init];
      }
      CCSprite *sprite = [CCSprite spriteWithImageNamed:@"res/gu_button.png"];
      sprite.position = [GameConfig convertPoint:ccp(viewSize.width, 160)];
      sprite.physicsBody.collisionType=@"aiCollision";
      sprite.physicsBody = [CCPhysicsBody bodyWithCircleOfRadius:sprite.contentSize.width/2 andCenter:ccp(sprite.contentSize.width/2, sprite.contentSize.height/2)];
      sprite.physicsBody.type = CCPhysicsBodyTypeDynamic;
      [_physicsNode addChild:sprite];
      [arrAI addObject:sprite];
  }
  </code></pre>
  
  <p>// -----------------------------------------------------------------------</p>
  
  <pre><code>-(void)update:(CCTime)delta{
      for (CCSprite *sp in arrPlayer) {
          sp.position= ccp(sp.position.x+playerSpeed, sp.position.y);
      }
      for (CCSprite *sp in arrAI) {
          sp.position= ccp(sp.position.x-aiSpeed, sp.position.y);
      }
  </code></pre>
  
  <p>implement delegate :</p>
  
  <pre><code>-(BOOL)ccPhysicsCollisionBegin:(CCPhysicsCollisionPair *)pair  playerCollision:(CCNode *)nodeA aiCollision:(CCNode *)nodeB{
      NSLog(@"Coll.");
  
  
  - (id)init
  {
      // Apple recommend assigning self with supers return value
      self = [super init];
      if (!self) return(nil);
  
      viewSize=CGSizeMake([GameConfig converPoint:480], [GameConfig converPoint:320]);
      _physicsNode = [CCPhysicsNode node];
      _physicsNode.collisionDelegate =self;
      _physicsNode.debugDraw =YES;
      _physicsNode.gravity=ccp(0, 0);
  </code></pre>
  
  <p>please let me know why " ccPhysicsCollisionBegin " never call
  thanks everyone</p>