Unity3D：计数带有特定GameObject标签的子代时出错

Question

Unity3D 2018.2.5

I have a GameObject called "MainObject" which has several other GameObjects as children called SideObjects under it with tags "High" and "Low". Since there are several different GameObjects in MainObject, I'm trying to count them.

I'm trying to count how many GameObjects are in "MainObject" with the tag "High".

This is the code I have so far in trying to get a tag from the children of a parent GameObject, but I get an error.

Error:

ArgumentException: GetComponent requires that the requested component 'List 1' derives from MonoBehaviour or Component or is an interface. UnityEngine.GameObject.GetComponentInChildren[List 1' derives from MonoBehaviour or Component or is an interface. UnityEngine.GameObject.GetComponentInChildren[List 1] (Boolean includeInactive) (at C:/buildslave/unity/build/Runtime/Export/GameObject.bindings.cs:70)

Code I have:

public void getListOfObjectsInMain()
{
    // Reset count before counting
    objCountInMain = 0;

    //  Count amount of children in camera transform
    GameObject currentMain = GameObject.FindGameObjectWithTag("MainCamera").GetComponent<HandleCamera>().targetToLookAt.gameObject;

     // Debug.Log(currentMain);

    List<GameObject> allObjectsInMain = currentMain.GetComponentInChildren<List<GameObject>>(false);

    foreach (GameObject obj in allObjectsInMain)
    {
        if (obj.gameObject.tag == "High")
        {
            objCountInMain++;
        }
    }

    //  Text
    objInMainText.text = objCountInMain.ToString();
}

Answer 1

Few issues:

1 . GameObject[] allObjectsInMain = currentMain.GetComponentInChildren

The GetComponentInChildren function is used to get one component from a GameObject. Tying to make it return an array or multiple objects would throw an exception.

2 . currentMain.GetComponentInChildren<List<GameObject>>(false);

You can't pass GameObject to the GetComponentInChildren function because GameObject is not the-same as a component. Components are attached to GameObjects and the GetComponentXXX functions only return Components not GameObject. Hence the Component key word in it.

Also you can't pass List to it. The only thing to pass to this function is a component or script that inherits from MonoBehaviour , an interface or any built-in component such as the Rigidbody component.

---

Use the GetComponentsInChildren function with s in it. That returns multiple Objects. Also, pass Transform to it since Transform is a component and every GameObject in the scene has a Transform component, it can be used to find all child objects.

int CountChildObjectsByTag(GameObject parent, string tag)
{
    int childCount = 0;
    Transform[] ts = parent.GetComponentsInChildren<Transform>();
    foreach (Transform child in ts)
    {
        if (child != parent.transform && child.CompareTag(tag))
            childCount++;
    }
    return childCount;
}

Even better, just loop over the transform . Now, you don't have to use GetComponentsInChildren or return an array each time this function is called.

int CountChildObjectsByTag(GameObject parent, string tag)
{
    int childCount = 0;
    foreach (Transform child in parent.transform)
    {
        if (child.CompareTag(tag))
            childCount++;
    }
    return childCount;
}

Usage:

GameObject currentMain = GameObject.FindGameObjectWithTag("MainCamera");
int childCount = CountChildObjectsByTag(currentMain, "High");