SpriteKit didBeginContact not being called - ios

Question

I hope you can help, have a block moving across and it jumps to avoid obstacles and collect coins.
It's collision with the obstacles is working correctly and the below gameOver is working correctly.
-(void)didBeginContact:(SKPhysicsContact *)contact
{
if ([contact.bodyA.node.name isEqualToString:#"coins"] || [contact.bodyB.node.name isEqualToString:#"coins"]) {
[self coinCollected]; //THIS IS NOT WORKING
NSLog(#"contacted"); //THIS IS NOT WORKING
}
else if ([contact.bodyA.node.name isEqualToString:#"ground"] || [contact.bodyB.node.name isEqualToString:#"ground"]) {
[hero land];
}
else {
NSLog (#"dead");
[self gameOver];
[self runAction:[SKAction playSoundFileNamed:#"gameover.wav" waitForCompletion:NO]];
}
}
My PMWorldGenenerator file looks as below:
#import "PMWorldGenerator.h"
#interface PMWorldGenerator ()
#property double currentGroundX;
#property double currentObstacleX;
#property double coinX;
#property SKNode *world;
#end
#implementation PMWorldGenerator
static const uint32_t obstacleCategory = 0x1 << 1;
static const uint32_t groundCategory = 0x1 << 2;
static const uint32_t coinCategory = 0x1 << 3;
+ (id)generatorWithWorld:(SKNode *)world {
PMWorldGenerator *generator = [PMWorldGenerator node];
generator.currentGroundX = 0;
generator.currentObstacleX = 400;
generator.coinX = 50;
generator.world = world;
return generator;
}
-(void)populate
{
for (int i = 0; i <3; i++)
[self generate];
}
-(void)generate
{
SKSpriteNode *ground = [SKSpriteNode spriteNodeWithColor:[UIColor greenColor] size:CGSizeMake(self.scene.frame.size.width, self.scene.frame.size.height/2.7)];
ground.name = #"ground";
ground.position = CGPointMake(self.currentGroundX, -self.scene.frame.size.height/2 + ground.frame.size.height/2);
ground.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:ground.size];
ground.physicsBody.categoryBitMask = groundCategory;
ground.physicsBody.dynamic = NO;
[self.world addChild:ground];
self.currentGroundX += ground.frame.size.width;
SKSpriteNode *obstacle = [SKSpriteNode spriteNodeWithColor:[UIColor redColor] size:CGSizeMake(10,10)];
obstacle.name = #"obstacle";
obstacle.position = CGPointMake(self.currentObstacleX/5, ground.position.y + ground.frame.size.height/2 + obstacle.frame.size.height/2 + 5);
obstacle.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:obstacle.size];
obstacle.physicsBody.dynamic = NO;
obstacle.physicsBody.categoryBitMask = obstacleCategory;
[self.world addChild:obstacle];
self.currentObstacleX += 550 ;
SKSpriteNode *coins = [SKSpriteNode spriteNodeWithColor:[UIColor yellowColor] size:CGSizeMake(4, 4)];
coins.name = #"coins";
coins.position = CGPointMake(self.coinX+80, ground.position.y + ground.frame.size.height/2 + obstacle.frame.size.height/2 + 25);
coins.physicsBody.categoryBitMask = coinCategory;
coins.physicsBody.dynamic = YES;
SKAction *revolution = [SKAction rotateByAngle:M_PI_4*10 duration:3];
SKAction *repeatRotate = [SKAction repeatActionForever:revolution];
[coins runAction:repeatRotate];
[self.world addChild:coins];
self.coinX += 550;
}
and lastly my PMHero file:
#import "PMHero.h"
#interface PMHero ()
#end
#implementation PMHero
static const uint32_t heroCategory = 0x1 << 0;
static const uint32_t obstacleCategory = 0x1 << 1;
static const uint32_t groundCategory = 0x1 << 2;
static const uint32_t coinCategory = 0x1 << 3;
+(id)hero
{
PMHero *hero = [PMHero spriteNodeWithColor:[UIColor redColor] size:CGSizeMake(12,12)];
hero.name = #"hero";
hero.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:hero.size];
hero.physicsBody.categoryBitMask = heroCategory;
hero.physicsBody.contactTestBitMask = obstacleCategory | groundCategory | coinCategory;
return hero;
}
I have done exactly what I had done for my obstacles and ground for the "coins", but it doesn't detect any collisions with them in my didBeginContact

Answer 1

You haven't added your physics body for coins
SKSpriteNode *coins = [SKSpriteNode spriteNodeWithColor:[UIColor yellowColor] size:CGSizeMake(4, 4)];
coins.name = #"coins";
coins.position = CGPointMake(self.coinX+80, ground.position.y + ground.frame.size.height/2 + obstacle.frame.size.height/2 + 25);
coins.physicsBody = [SKPhysicsBody bodyWith...//need code here
coins.physicsBody.categoryBitMask = coinCategory;
coins.physicsBody.dynamic = NO;
coins.physicsBody.collisionBitMask = 0;
SKAction *revolution = [SKAction rotateByAngle:M_PI_4*10 duration:3];
SKAction *repeatRotate = [SKAction repeatActionForever:revolution];
[coins runAction:repeatRotate];
[self.world addChild:coins];