How to Implement a Simple Traffic Light System in C# Using Coroutines

Learn how to effectively create a simple traffic light system in C# for Unity, ensuring smooth transitions between red and green lights.
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This video is based on the question https://stackoverflow.com/q/70295777/ asked by the user 'smonk' ( https://stackoverflow.com/u/16837421/ ) and on the answer https://stackoverflow.com/a/70295820/ provided by the user 'Nathan' ( https://stackoverflow.com/u/15095397/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding Traffic Light Scripts in C#

Creating a simple traffic light system using C# is a fun and educational way to get familiar with both Unity and coroutines. If you're new to coding in C# or Unity, you might run into a common issue where nothing happens when you run your script. This guide aims to explain why your traffic light script isn't functioning as expected and how to properly implement it for smooth light transitions.

The Problem: Why Doesn't the Light Change?

Initially, you may have a script that looks like this:

[[See Video to Reveal this Text or Code Snippet]]

In this script, you may notice that the light doesn't change color as intended. While the script doesn't throw compile errors, the lights will not switch due to how and where the coroutine is started.

The Solution: Properly Implementing Coroutines

To resolve this issue, you need to make a few adjustments to the way you initiate the coroutine. Below, I'll break down the necessary changes step by step:

Start Coroutine Outside of Update

Starting a coroutine within the Update() function is problematic. This is because Update() is called every frame, which means you're trying to start a new coroutine every single frame, leading to multiple loops trying to run concurrently. Here’s what you should do instead:

Start the Coroutine in the Start() Method: This ensures that the light switching logic runs only once when the game starts.

Adjust the Coroutine Logic

You also need to yield after each light switch to ensure that there’s a pause before the next action. Here’s the corrected version of the script:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Changes

Starting the Coroutine: By moving StartCoroutine(switchLight()); to the Start() method, we ensure that the light switches happen as intended, instead of attempting to start multiple instances of the coroutine from Update().

Yield After Each Switch: Adding yield return new WaitForSeconds(5); after both switch actions ensures that the lights remain in their state for 5 seconds before switching again. Without this, the lights would toggle almost immediately, leading to erratic behavior.

Conclusion

By applying these changes, you can create a simple traffic light system in C# that efficiently changes the lights between red and green. Understanding the flow of coroutines and how to manage them within Unity is crucial for building more complex systems in your games. Next time you're coding a similar feature, remember to consider where to start your coroutines and ensure you're yielding properly to give your code the time it needs to execute smoothly.

With practice and adjustments like these, you’ll surely take your C# coding skills to the next level! Happy coding!

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