Tags

Part of the Unity Scripting Basics section of Coddy's Unity journey. Lesson 57 of 85.

A tag is a label you give an object in the Inspector, picked from the list in the Tag Manager. Unity starts with a few (Player, MainCamera, Respawn, Finish and others) and you add your own. Many objects can share a tag, so tags group objects by role: every enemy, every coin, whatever each one is named. Three calls use them:

GameObject.FindWithTag("Player") returns one active object with the tag, or null.
GameObject.FindGameObjectsWithTag("Enemy") returns an array of every active object with the tag.
obj.CompareTag("Enemy") says whether one object has the tag.

This wave counter logs how many enemies the level starts with, however they are named:

void Start()
{
    GameObject[] enemies = GameObject.FindGameObjectsWithTag("Enemy");
    Debug.Log("Enemies left: " + enemies.Length);
}

A tag must exist in the Tag Manager: FindGameObjectsWithTag("Enemey") throws UnityException: Tag: Enemey is not defined. To test one object, prefer CompareTag("Enemy") to tag == "Enemy": it is faster, and it reports a tag that does not exist instead of quietly answering false.

Challenge

Medium

Light every street lamp when Space is pressed.

Inside the Space if, get GameObject[] lamps = GameObject.FindGameObjectsWithTag("Lamp");.
In foreach (GameObject lamp in lamps), set lamp.GetComponent<Renderer>().material.color = Color.yellow;.

Press Play and press Space: every lamp turns yellow, and the ball does not. Then Check.

Try it yourself

using UnityEngine;

public class StreetLights : MonoBehaviour
{
    void Update()
    {
        if (Input.GetKeyDown(KeyCode.Space))
        {
            // Turn every object tagged Lamp yellow.
        }
    }
}