Unity中TowerNode脚本找不到Shop脚本引发空引用异常求助

Let's break down why you're hitting that NullReferenceException and fix it step by step:

Root Cause #

The error happens because your shop variable in TowerNode is null when you try to call shop.Enable(). Looking at your Start() method:

shop = GetComponent<Shop>();
GameObject.Find("Shop");

• GetComponent<Shop>() tries to find a Shop component on the same GameObject as TowerNode—but your Shop script is attached to a separate GameObject named "Shop" (since you're calling GameObject.Find("Shop")).
• You call GameObject.Find("Shop") but don't assign its Shop component to the shop variable, so the variable stays null.

Also, you have a bug in OnMouseDown(): you're declaring a local bool IsShopOpen = true; which overrides the class-level IsShopOpen field. This means your check if (IsShopOpen == true) will always be true, regardless of the actual state.

Fixes #

1. Correctly Assign the Shop Reference

Update the Start() method in TowerNode to properly get the Shop component from the "Shop" GameObject:

void Start() {
 rend=GetComponent<Renderer>();
 startColor = rend.material.color;
 buildManager = BuildManager.instance;
 // Replace the old shop assignment with this
 GameObject shopObj = GameObject.Find("Shop");
 if (shopObj != null) {
     shop = shopObj.GetComponent<Shop>();
 } else {
     Debug.LogError("Couldn't find GameObject named 'Shop' in the scene!");
 }
}

2. Fix the IsShopOpen Variable Shadowing

In OnMouseDown(), remove the local variable declaration so you use the class-level IsShopOpen:

void OnMouseDown() {
 // Remove this line: bool IsShopOpen = true;
 IsShopOpen = true; // Set the class-level variable instead
 if (IsShopOpen == true) {
     if (shop != null) { // Add a safety check to avoid future null errors
         shop.Enable();
     } else {
         Debug.LogWarning("Shop reference is null, can't enable shop!");
     }
 }
 // ... rest of your code
}

Optional: Use a Singleton for Shop (More Reliable)

Just like your BuildManager uses a singleton, you can add one to Shop for easier, more reliable access:
Update your Shop script:

public class Shop : MonoBehaviour {
    public static Shop instance; // Add this singleton instance

    public TurretBlueprint Archery;
    // ... rest of your fields

    void Start() {
        // Set up the singleton
        if (instance == null) {
            instance = this;
        } else {
            Destroy(gameObject);
        }
        buildManager = BuildManager.instance;
        disableAllButtons();
        //Enable();
    }

    // ... rest of your methods
}

Then in TowerNode's Start(), you can get the Shop instance like this (no need for GameObject.Find):

shop = Shop.instance;

This is better because it avoids relying on GameObject names, which can break if you rename the Shop object later.

Final Notes #

• Always add null checks when accessing components you get from other GameObjects—this helps catch issues early and gives clearer debug messages.
• Make sure the GameObject named "Shop" actually exists in your scene and has the Shop script attached to it.

内容的提问来源于stack exchange，提问作者Lian Levi