dotween-upm-fork/UnityExamples.Unity5/Assets/Follow.cs

using UnityEngine;
using System.Collections;
using DG.Tweening;

public class Follow : MonoBehaviour
{
	public Transform target; // Target to follow
	Vector3 targetLastPos;
	Tweener tween;

	void Start()
	{
		// First create the "move to target" tween and store it as a Tweener.
		// In this case I'm also setting autoKill to FALSE so the tween can go on forever
		// (otherwise it will stop executing if it reaches the target)
		tween = transform.DOMove(target.position, 2).SetAutoKill(false);
		// Store the target's last position, so it can be used to know if it changes
		// (to prevent changing the tween if nothing actually changes)
		targetLastPos = target.position;
	}

	void Update()
	{
		// Use an Update routine to change the tween's endValue each frame
		// so that it updates to the target's position if that changed
		if (targetLastPos == target.position) return;
		// Add a Restart in the end, so that if the tween was completed it will play again
		tween.ChangeEndValue(target.position, true).Restart();
		targetLastPos = target.position;
	}
}