SpriteKit didBeginContact issue with 2 non dynamic bodies - ios7

Question

I'm trying to create a game with blocks that can be moved around they all belong to the same categoryBitMask. The didBeginContact does not fire unless I set the physicsBody to dynamic. How can I detect collision between two blocks that belong to the same category?
Code for generating blocks:
float blkX = 34;
float blkY = 64;
for (int i = 0; i < 4; i++) {
for (int j = 0; j < 6; j++){
block = [SKSpriteNode spriteNodeWithImageNamed:blocksArray[(arc4random()%5)]];
block.position = CGPointMake(blkX, blkY);
block.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:block.size];
block.physicsBody.usesPreciseCollisionDetection = YES;
block.physicsBody.dynamic = NO;
block.physicsBody.categoryBitMask = blockCategory;
block.physicsBody.contactTestBitMask = blockCategory;
block.physicsBody.collisionBitMask = blockCategory;
[block setName:#"block"];
[_bgLayer addChild:block];
blkX += 48;
}
blkX = 34;
blkY += 48;
}
I am using the SKPhysicsContactDelegate and have the following two lines in my init method:
self.physicsWorld.contactDelegate = self;
self.physicsWorld.gravity = CGVectorMake(0.0, 0.0);
My didBeginContact method:
-(void)didBeginContact:(SKPhysicsContact *)contact{
SKPhysicsBody *firstBody, *secondBody;
firstBody = contact.bodyA;
secondBody = contact.bodyB;
NSLog(#"We Collided!");
}
Any help appreciated. Thanks!

Answer 1

I did come up with something that does work for those in a similar situation:
In my touchesBegan method I set the block being moved to be Dynamic which does fire the didBeginContact. Here is my touchesBegan method:
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
self.selectedNode = [self nodeAtPoint:[[touches anyObject] locationInNode:self]];
[self.selectedNode.physicsBody setDynamic:YES];
}
Then you turn it off again in the touchesEnded method.
I also set the block.physicsBody.collisionBitMask = 0 which allows the block to move through other blocks. If this helps at least one other person then it was worth asking the question!