Increase speed with each enemy destroyed?

Question

I need some help with coding this idea: "For each Target destroyed, increase the Gunner's speed by (speed variable)". The idea is that the Gunner is automatically moving, and I want it to become more frantic with each target hit.

Here's the relevant code I have so far:

   using UnityEngine;
   using System.Collections;
   using System.Collections.Generic;

    void Update () {
            Gunner_Move (); 
    }


    //gives me the error "Assets/_Scripts/MovementPathScript.cs(60,83): error CS0200: Property or indexer `System.Array.Length' cannot be assigned to (it is read only)"
    void Gunner_Move(){
            if (GameObject.FindGameObjectsWithTag ("BulletProgressionObject").Length -= 1)
                Gunner_SpeedIncrease ();
    }

void Gunner_SpeedIncrease(){ //behavior that I'm not sure how to make }

    //for the bullets colliding with target's parent object
        void OnTriggerEnter(Collider other){
            if (other.gameObject.CompareTag ("BulletProgressionObject"))
                Destroy (other.gameObject);

I think it's a foreach loop, but the issue I'm having is properly implementing it. Any suggestions or referrals would be greatly appreciated.

Answer 1

Rather than calling GameObject.FindGameObjectsWithTag every frame, you could just call Gunner_SpeedIncrease() within OnTriggerEnter when the trigger/collision happens.

void OnTriggerEnter(Collider other) {
    if (other.gameObject.CompareTag ("BulletProgressionObject")) {
        Destroy (other.gameObject);
        Gunner_SpeedIncrease ();
    }
}