Unity中的运行时错误可能会破坏随机方向变化

Question

Good day

I am writing one of my first unity programs, and I am getting an error that does not make sense to me. I have a character on the screen that I move in a random direction when the game starts. The character always seems to move in the same direction however despite the fact that I am randomizing the value.

I intend to change the direction randomly as soon as a limit is reached as well, but this does not seem to work either. The direction never seems to change, and I am wondering if it is due to an run time error that I am receiving.

The error is telling me that the RigidBody variable inside my class is not set. I know I set it, and the fact that my character moves tells me it is finding the rigid body component.

My code looks like this:

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

public class Unit : MonoBehaviour {

    // Use this for initialization
    int direction;
    public Rigidbody2D rb;
    int speed = 5;
    int maxX = 6;
    int minX = -6;
    int maxY = 4;
    int minY = -4;
    void Start () {
        randomDirection();
    }

    void randomDirection()
    {
        System.Random rand = new System.Random(Guid.NewGuid().GetHashCode());

        int temp = -1;

        while(temp != direction)
        {
            temp = rand.Next(0, 4);
        }

        direction = temp;

        switch (direction)
        {
            case 0:
                rb.velocity = new Vector2(-speed, 0);
                break;
            case 1:
                rb.velocity = new Vector2(speed, 0);
                break;
            case 2:
                rb.velocity = new Vector2(0, -speed);
                break;
            case 3:
                rb.velocity = new Vector2(0, speed);
                break;
        }
    }

    // Update is called once per frame
    void Update () {        

        if (transform.position.x >= maxX || transform.position.y >= maxY || transform.position.y <= minX || transform.position.y <= minY)
        {
            randomDirection();           
        }

        Vector2 pos = transform.position;
        pos.x = Mathf.Clamp(pos.x, -maxX, maxX);
        pos.y = Mathf.Clamp(pos.y, -maxY, maxY);
        transform.position = pos;
    }
}

Here is a screenshot of my inspector showing that rb (my RigidBody variable) is set:

Here is the error that I am receiving:

UnassignedReferenceException: The variable rb of Unit has not been assigned. You probably need to assign the rb variable of the Unit script in the inspector. UnityEngine.Rigidbody2D.set_velocity (Vector2 value) (at C:/buildslave/unity/build/artifacts/generated/common/modules/Physics2D/Physics2DBindings.gen.cs:2060) Unit.randomDirection () (at Assets/Scripts/Unit.cs:36) Unit.Start () (at Assets/Scripts/Unit.cs:17)

I am not sure if I am checking whether the limit is being reached correctly. I am using the clamp command to restrict the unit to the limits of my screen. I put a debug in the if statement that checks my limit, and it seems to reach it, but still no direction change.

Any advice would be greatly appreciated. Thanks in advance!

Answer 1

You get this error when your script is likely attached to multiple GameObjects or the-same GameObject twice and the variable is not assigned in the other object is is attached to.

With your screenshot, it is attached to the-same GameObject twice. The first one has a Rigidbody plugged into the rb variable slot. The second one doesn't. Remove the one Unit script which is above the Rigidbody component as that's the one that doesn't have anything assigned to the rb variable.

This is how to remove it: