title: How do I implement enemies that shoot?
body: <p>I made a game with SpriteKit. I structured my game by coding a GameScene (SKScene) and a separate enemy class. 
  I want the spawning enemies to shoot a particle e.g. every 2 seconds (just moving an SKEmitterNode by the y axis) I tried to do it with a timer, but it doesn't really work. </p>
  
  <p>I call my Enemy class from the gaming Scene with this code:</p>
  
  <p><strong>GameScene.m</strong></p>
  
  <pre><code> -(void)enemiesLevel1{
      EnemyClass* wave1 = [[EnemyClass alloc] init];
      [wave1 enemiesLevel1:self];
   }
  </code></pre>
  
  <p>And I am basically calling this method from <strong>EnemyClass.m</strong></p>
  
  <pre><code>-(void)enemiesLevel1:(SKScene *)scene
  {
      enemy = [SKSpriteNode spriteNodeWithImageNamed:Enemy];
      //Enemy Path
      (...)
  
      SKAction *followPath2 = [SKAction followPath:pathRef2
                                          asOffset:NO
                                      orientToPath:YES
                                          duration: pathSpeed];
  
  
  
  
      SKAction *forever = [SKAction repeatActionForever:followPath2];
  
  
  
      //PhysicsBody Eigenshaften
      enemy.physicsBody =[SKPhysicsBody bodyWithCircleOfRadius:enemy.size.width];
      enemy.physicsBody.dynamic = YES;
      enemy.physicsBody.categoryBitMask = enemyCategory;
  
      [enemy runAction:forever];
      [scene addChild:enemy];
  
      NSTimer *timer;
      timer = [NSTimer scheduledTimerWithTimeInterval:0.5
                                           target:self
                                         selector:@selector(weaponParticle)
                                         userInfo:nil
                                          repeats:YES];
      }
  
  
  
  
  -(void)weaponParticle{
  
  
      screenHeight = self.frame.size.height;
      screenWidth = self.frame.size.width;
  
      //Schuss-Particles
  
      enemyParticlePath = [[NSBundle mainBundle] pathForResource:@"ShootFire" ofType:@"sks"];
      enemyParticle = [NSKeyedUnarchiver unarchiveObjectWithFile:enemyParticlePath];
  
      enemyParticle.physicsBody =[SKPhysicsBody bodyWithCircleOfRadius:0.2];
      enemyParticle.physicsBody.categoryBitMask = shootCategory;
      enemyParticle.physicsBody.contactTestBitMask = playerCategory;
  
      //Schuss-Action
      moveDown = [SKAction moveByX:0.0 y:-screenHeight duration:1.0];
      remove = [SKAction removeFromParent];
      weaponShot = [SKAction sequence:@[moveDown, remove]];
  
      enemyParticle.position = CGPointMake(enemy.position.x, enemy.position.y+10);
  
  
  
      [self addChild:enemyParticle];
      [enemyParticle runAction: weaponShot];
  
  }
  </code></pre>
  
  <p>The enemies are spawning 1 by 1 just how I wanted, but they can't shoot. Can anyone help me out?</p>