Sword shooting Eggs or Snowballs

Hey guys, I need a little help with Swords shooting Snowballs or eggs I have some code and Here it is, Please help though

<?php

namespace sm11\IronCannon;
use pocketmine\plugin\PluginBase;
use pocketmine\event\Listener;
use pocketmine\Plugin;
use pocketmine\Player;
use pocketmine\event\entity\EntityDamageEvent;
use pocketmine\event\entity\EntityDamageByEntityEvent;

class Main extends PluginBase implements Listener{

public function onEnable(){
$this->getServer()->getPluginManager()->registerEvents($this, $this);
$this->getLogger()->info("IronCannon enabled!");
}

public function onDisable(){
$this->getLogger()->info("IronCannon disabled!");
}

public function onDamage(EntityDamageEvent $event){
if($event instanceof EntityDamageByEntityEvent){
$a = $event->getDamager();
$item = $a->getInventory()->getItemInHand();
if($a instanceof Player){
if($item == 276){
$event->setCancelled(true);
//Code to shoot snowball
}
}
}
}
}

http://docs.pocketmine.net/db/dc9/classpocketmine_1_1entity_1_1_snowball.html

On Damage?
Better would be onInteract:

PHP:

public function onScreenHold(PlayerInteractEvent $event){
$player = $event->getPlayer();
$item = $this->getPlayer()->getInventory()->getItemInHand();
($event->getBlock()->getId() === 0 ?: return);
if($item->getId() == Item::IRON_SWORD){
// Code to shoot snowball
// Sorry dont have time for it now :)
}
}


oh Thanks