Please don’t double post as noted by @MelvMay in your duplicate post.
If you post a code snippet, ALWAYS USE CODE TAGS:
How to use code tags: Using code tags properly
Understand the steps involved:
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detecting the trigger (millions of tutorials… prove this occurs with a simple Debug.Log())
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doing “some stuff” when the trigger happens (again, lots of tutorials for single lights)
Part 1 doesn’t change with 1 or 20 lights.
Part 2 does change: get familiar with collections (arrays / lists) of lights, and how to iterate them. Then you create a list of Light references, iterate them and turn them all on / off.
Look up tutorials on collections (arrays / lists) in general (C#), and specifically how it works in the Unity context.
When debugging, keep this in mind:
You must find a way to get the information you need in order to reason about what the problem is.
What is often happening in these cases is one of the following:
- the code you think is executing is not actually executing at all
- the code is executing far EARLIER or LATER than you think
- the code is executing far LESS OFTEN than you think
- the code is executing far MORE OFTEN than you think
- the code is executing on another GameObject than you think it is
To help gain more insight into your problem, I recommend liberally sprinkling Debug.Log() statements through your code to display information in realtime.
Doing this should help you answer these types of questions:
- is this code even running? which parts are running? how often does it run? what order does it run in?
- what are the values of the variables involved? Are they initialized? Are the values reasonable?
- are you meeting ALL the requirements to receive callbacks such as triggers / colliders (review the documentation)
Knowing this information will help you reason about the behavior you are seeing.
You can also put in Debug.Break() to pause the Editor when certain interesting pieces of code run, and then study the scene
You could also just display various important quantities in UI Text elements to watch them change as you play the game.
If you are running a mobile device you can also view the console output. Google for how on your particular mobile target.
Another useful approach is to temporarily strip out everything besides what is necessary to prove your issue. This can simplify and isolate compounding effects of other items in your scene or prefab.
Here’s an example of putting in a laser-focused Debug.Log() and how that can save you a TON of time wallowing around speculating what might be going wrong: