how to make enemy sprite shoot at player - ios

Question

I'm using a sprite kit to create a game.
I have a player node which I control by touch but then I have an enemy node that moves on its own. I need the enemy to be able to shoot projectiles on its own. I'm guessing I would need a method for this and to call it. I need the direction of the projectiles to shoot wherever my player is. Any suggestions?
Here is the method I have:
-(void)monstershoot
{
SKSpriteNode * projectile = [SKSpriteNode spriteNodeWithImageNamed:#"projectile"];
projectile.position = _enemy.position;
CGPoint offset = rwSub(_player.position, projectile.position);
if (offset.x <= 0) return;
[_background addChild:projectile];
CGPoint direction = rwNormalize(offset);
CGPoint shootAmount = rwMult(direction, 1000);
CGPoint realDest = rwAdd(shootAmount, projectile.position);
// 9 - Create the actions
float velocity = 480.0/1.0;
float realMoveDuration = self.size.width / velocity;
SKAction * actionMove = [SKAction moveTo:realDest duration:realMoveDuration];
SKAction * actionMoveDone = [SKAction removeFromParent];
[projectile runAction:[SKAction sequence:#[actionMove, actionMoveDone]]];
}
But nothing happens when I call it.

Answer 1

It will do "nothing" in two cases: the image doesn't exist or the enemy is right of the player. Replace this line
if (offset.x <= 0) return;
by a check if the length of the offset vector is 0. You could write a method to calculate the length by using
sqrtf(powf(offset.x,2) + powf(offset.y,2))
Further you should use the length of shootAmount to calculate
float realMoveDuration = 1000 / velocity;
which will give you the same (and correct) speed for every projectile. But otherwise I see nothing wrong with your code.