setting a transform var to an object that collided

I just want the object to identify surrounding objects inside a collider and i thought of this script (C Sharp) to do so:

using UnityEngine;
using System.Collections;

public class generatorScript : MonoBehaviour {

	Transform structureLink;
	// Use this for initialization
	void Start () {
	// Update is called once per frame
	void Update () {
	void OnCollisionEnter (Collision[] hit) {
		for (int i = 0; i < hit.Length; i++){
			if (hit*.transform.tag =="structure"){*

_ structureLink = hit*.transform;*_

* }*
* }*

* }*

anyway there is a warning that says: Assets/generatorScript.cs(6,19): warning CS0414: The private field `generatorScript.structureLink’ is assigned but its value is never used
and an error that says:Script error: OnCollisionEnter
This message parameter has to be of type: Collision
The message will be ignored.
any help is much apriciated thank you

OnCollisionEnter() has a collision as a parameter, not an array of collisions. If your object first collides with multiple object in a single frame, you will get multipe OnCollisionEnter() calls during that frame, one for each object you collided with. A collision has the transform of the object you collided with.

void OnCollisionEnter (Collision collision) {
        if (  =="structure"){
             structureLink = collision.transform;