MovingTest.cs

using UnityEngine;
using System.Collections;

[RequireComponent (typeof(Rigidbody))]
public class MovingTest : MonoBehaviour {

    [SerializeField] float moveSpeed = 10f;

    [SerializeField] bool a = true;

    Transform trans;

    Rigidbody rig;

    void Awake()
    {
        trans = transform;
        rig = rigidbody;
    }

    void Update()
    {
        float moveHorizontal = Input.GetAxis("Horizontal");
        float moveVertical = Input.GetAxis("Vertical");
        rig.velocity = new Vector3(moveHorizontal * moveSpeed, 0, moveVertical * moveSpeed);

        if (a)
        {
            rig.position = new Vector3
                (
                    Mathf.Clamp(rig.position.x, -1, 1),
                    0.0f,
                    Mathf.Clamp(rig.position.z, 0, 10)
                );
        }
        else
        {
            trans.localPosition = new Vector3
                (
                    Mathf.Clamp(trans.localPosition.x, -1, 1),
                    0.0f,
                    Mathf.Clamp(trans.localPosition.z, 0, 10)
                );
        }
    }

}