Unity C# Cheat Sheet

UnityCodingCheatSheet.txt

// Unity C# Cheat Sheet
// I made these examples for students with prior exerience working with C# and Unity. 
// Too much? Try Unity's very good tutorials to get up to speed: https://unity3d.com/learn/tutorials/topics/scripting

AudioExamples.cs

// Various audio examples for Unity
using UnityEngine;
using System.Collections;

public class AudioExamples : MonoBehaviour
{
    // Important: You need to have an AudioSource component attached to this gameObject
    private AudioSource audioSource;

    // Set an audioclip in the Inspector
    public AudioClip clip1;

    void Start()
    {
        // Get the AudioSource component
        audioSource = GetComponent<AudioSource>();

        // Plays the AudioClip set in the AudioSource component. Will be interrupted if the function is called again.
        audioSource.Play();
    }

    void Update()
    {
        // AudioSource.Play() can also be paused or stopped. 
        // Check if audioSource is playing a clip. Jump is space and Fire1 is left ctrl.
        if (audioSource.isPlaying)
        {
            if (Input.GetButtonDown("Jump"))
            {
                audioSource.Pause();
            }
            else if (Input.GetButtonDown("Fire1"))
            {
                audioSource.Stop();
            }
        }

        // PlayOneShot can be used to play a short clip. Will not be interrupted if the function is called again. 
        // Can't be used with Pause & Stop. Fire2 is left alt in the Input Manager.
        if (Input.GetButtonDown("Fire2"))
        {
            audioSource.PlayOneShot(clip1);

            // You can give this an optional volume setting as well (0-1 range)
            //audioSource.PlayOneShot(clip1, 0.5f);
        }

        // Fire3 is left shift
        if (Input.GetButtonDown("Fire3"))
        {
            // Set the pitch and volume of the clips played by Audio Source. Volume range is 0~1
            audioSource.pitch = Random.Range(0.25f, 2f);

            audioSource.volume = Random.Range(0.25f, 1f);
        }
    }
}

Collision2DExamples.cs

// Various 2D collision examples
using UnityEngine;
using System.Collections;

public class Collision2DExamples : MonoBehaviour
{
    // Collisions/Triggers require a collider component on both gameObjects and a rigidbody on at least one.
    // Collision = physics. Trigger = overlap.

    void OnCollisionEnter2D(Collision2D other)
    {
        // Do something when another collider touches this gameObject's collider
        Debug.Log("Collided with something");

        // Conditional statements can be used to filter collisions/triggers. Checking for a known tag is one option. Be sure to define tag in the Inspector or you will get an error.
        if (other.gameObject.CompareTag("tag1"))
        {
            Debug.Log("tag1 collision");
        }
        else if (other.gameObject.CompareTag("tag2"))
        {
            Debug.Log("tag2 collision");
        }
    }

    // Is Trigger needs to be selected on one of the colliders
    void OnTriggerEnter2D(Collider2D other)
    {
        // Do something if another collider overlaps this gameObject's collider
        Debug.Log("Triggered by something");
    }

    // Collision and Trigger also have exit and stay events
    void OnCollisionExit2D(Collision2D other)
    {
        // Do something after a collider is no longer touching this gameObject's collider
        Debug.Log("Collision ended");
    }

    void OnTriggerStay2D(Collider2D other)
    {
        // Do something while a collider is still overlapping with this gameObject's collider
        Debug.Log("Still triggering");
    }

}

EnableSetActiveExamples.cs

// Various ways of enabling/disabling a gameObject's components and activating/deactivating a gameObject.
using UnityEngine;
using System.Collections;

public class EnableSetActiveExamples : MonoBehaviour
{
    public GameObject targetGameObject;
    private Collider2D coll2D;

    void Start()
    {
        // SetActive can switch a gameObject on or off in the Hierarchy. Once deactivated, its components will no longer run until reactivated.
        targetGameObject.SetActive(false);

        // Get a collider2D component attached to this gameObject. Note: Collider2D will work with any kind of 2D collider component.
        coll2D = GetComponent<Collider2D>();

        // Disable or enable a component using a bool
        coll2D.enabled = false;
    }

    // Update is called once per frame
    void Update()
    {
        // Jump is space in Input Manager
        if (Input.GetButtonDown("Jump"))
        {
            // Check if a gameObject is active in the scene with activeInHierarchy. Reminder: The ! is shorthand for == false. If the gameObject is inactive, activate it
            if (!targetGameObject.activeInHierarchy)
            {
                targetGameObject.SetActive(true);
            }
        }

        // Fire1 is left ctrl in Input Manager
        if (Input.GetButtonDown("Fire1"))
        {
            // Check if a component is enabled. Reminder: The ! is shorthand for == false.
            if (!coll2D.enabled)
            {
                coll2D.enabled = true;
            }
        }
    }
}

FindExamples.cs

// Various ways of finding things in Unity

using UnityEngine;
using System.Collections;

public class FindExamples : MonoBehaviour
{
    // Example needs a Rigidbody2D component to work
    private Rigidbody2D rb2D, otherRb2D, childRb2D;
    private GameObject hierarchyObject, childObject, taggedObject;

    void Start()
    {
        // Find a component attached to this GameObject
        rb2D = GetComponent<Rigidbody2D>();

        // Find a GameObject in the Hierarchy. NOTE: This will check all GameObjects in the Hierarchy! Proceed with caution...
        hierarchyObject = GameObject.Find("Name Of Object");
        
        // Find a GameObject in the hierarchy based on tag. NOTE: Fast than finding by name since it only needs to check GameObjects with the matching tag.
        taggedObject = GameObject.FindWithTag("Player");
        
        // Can be combined to find a component on a GameObject in the Hierarchy
        otherRb2D = GameObject.FindWithTag("Player").GetComponent<Rigidbody2D>();

        // Lowercase transform.Find can be used to search child GameObjects by name
        childObject = transform.Find("Name Of Object").gameObject;

        // Can also be combined
        childRb2D = transform.Find("Name Of Object").GetComponent<Rigidbody2D>();
    }
}

IEnumeratorExamples.cs

// Various IEnumerator timer examples for Unity
using UnityEngine;
using System.Collections;

public class IEnumeratorExamples : MonoBehaviour
{
    // Flag for checking if a coroutine is running
    private bool alreadyDelayed;

    // Necessary to stop a coroutine
    private IEnumerator coroutine;

    void Start()
    {
        // Coroutines run in Start are only called once. No if statement + bool needed.
        StartCoroutine(LoopingTimer(7f));

        // Set to an IEnumerator
        coroutine = LoopingTimer(1f);
        StartCoroutine(coroutine);
    }

    void Update()
    {
        // Left ctrl key is Fire1 in Input Manager
        if (Input.GetButtonDown("Fire1"))
        {
            StartCoroutine(DelayTimerOneShot(1f));
        }

        // Space bar is Jump in Input Manager
        if (Input.GetButtonDown("Jump"))
        {
            // This if statement ensures that a coroutine can't be run again if it is already running.
            if (!alreadyDelayed)
            {
                StartCoroutine(DelayTimerLatching(3f));
            }
        }

        // Left alt is Fire2 in Input Manager.
        if (Input.GetButtonDown("Fire2"))
        {
            // To stop a coroutine...
            StopCoroutine(coroutine);
            Debug.Log("Stopped at " + Time.time);
        }
    }

    // Wait for an amount of time before doing something (one shot behavior)
    private IEnumerator DelayTimerOneShot(float delayLength)
    {
        yield return new WaitForSeconds(delayLength);
        // Do something
        Debug.Log("Delayed One Shot");
    }

    // Wait for an amount of time before doing something (latching behavior)
    private IEnumerator DelayTimerLatching(float delayLength)
    {
        // Set the already delayed flag to signal that this coroutine is already running
        alreadyDelayed = true;
        // Do something 
        Debug.Log("Delayed Latch");
        yield return new WaitForSeconds(delayLength);
        // Do something
        Debug.Log("Delayed Latch Released");
        // Reset the already delayed flag so that this coroutine can be used once again.
        alreadyDelayed = false;
    }

    // Sequence of delays
    private IEnumerator DelayTimerSequence(float delayLength1, float delayLength2)
    {
        alreadyDelayed = true;
        yield return new WaitForSeconds(delayLength1);
        // Do first thing
        Debug.Log("First Delay");
        yield return new WaitForSeconds(delayLength2);
        // Do second thing
        Debug.Log("Second Delay");
        alreadyDelayed = false;
    }

    // This creates an endless loop
    private IEnumerator LoopingTimer(float loopInterval)
    {
        while (true)
        {
            // Do something
            Debug.Log("Repeat");
            yield return new WaitForSeconds(loopInterval);
        }
    }
}

InputExamples.cs

// Various examples of Input usage in Unity
using UnityEngine;
using System.Collections;

public class InputExamples : MonoBehaviour
{
    // These strings need to be set in the Inspector to match Input Manager entries
    public string horiAxis, vertAxis, jump, button1, button2;

    public KeyCode key1;

    public Vector2 speed = new Vector2(10f, 5f);

    void Update()
    {
        // Run only once when button is pressed
        if (Input.GetButtonDown(jump))
        {
            Debug.Log("Jump");
        }
        // Keep running while button is held down
        if (Input.GetButton(button1))
        {
            Debug.Log("Fire1");
        }
        // Run only once when the button is released
        if (Input.GetButtonUp(button2))
        {
            Debug.Log("Fire2");
        }

        // Input.GetAxis will return a number between -1 and 1, with smoothing applied (adjust Sensitivity in Input Manager)
        Debug.Log("Horizontal: " + Input.GetAxis(horiAxis));

        // Input.GetAxisRaw will return a number between -1 and 1, without Sensitivity smoothing applied
        Debug.Log("Vertical: " + Input.GetAxisRaw(vertAxis));

        // This is often multiplied by a number to create movement
        Debug.Log("Horizontal Modified: " + Input.GetAxis(horiAxis) * speed.x);

        // Key pressed down
        if (Input.GetKeyDown(KeyCode.T))
        {
            Debug.Log("Key T pressed");
        }

        // Key held down
        if (Input.GetKey(KeyCode.Y))
        {
            Debug.Log("Key A pressed");
        }

        // KeyCode can also be set in the Inspector as a variable
        if (Input.GetKeyUp(key1))
        {
            Debug.Log("Key released");
        }
    }
}

InstantiateExamples.cs

// Various Instantiate examples for Unity
using UnityEngine;
using System.Collections;

public class InstantiateExamples : MonoBehaviour
{
    // Set the object to be cloned in the Inspector. Be sure to use a Prefab from Project NOT Scene!
    public GameObject prefab;

    // Set a target transform in the Inspector to clone prefab from
    public Transform spawnPoint;

    // Update is called once per frame
    void Update()
    {
        // Basic cloning
        if (Input.GetButtonDown("Jump"))
        {
            // Pass the prefab as an argument and clone it at the transform of this gameObject. 
            Instantiate(prefab, transform);

            // Second argument could be set to different transform, if there is another place the prefab should be cloned.
            //Instantiate(prefab, spawnPoint);
        }

        // Advanced cloning
        if (Input.GetButtonDown("Fire1"))
        {
            // Overloaded method which can be positioned and rotated. 
            GameObject p = Instantiate(prefab, transform.position, Quaternion.identity) as GameObject;

            // Make this clone a child of the gameObject that spawned it
            p.transform.parent = transform;

            // This approach allows you to further manipulate the cloned prefab in this script. Such as...
            // Destroying the clone after a set amount of time
            Destroy(p, 3f);

            // Accessing the cloned prefab's components. Note: The prefab needs a Rigidbody2D component for the next 2 lines to work.
            Rigidbody2D pRB2D = p.GetComponent<Rigidbody2D>();
            pRB2D.AddForce(Vector2.up * 100f);
        }

        // Clone prefab at specified transform
        if (Input.GetButtonDown("Fire2"))
        {
            GameObject p = Instantiate(prefab, spawnPoint.position, Quaternion.identity) as GameObject;
            p.transform.parent = transform;
        }
    }
}

SceneManagementExamples.cs

// Various examples of scene management for Unity 5+
using UnityEngine;
using System.Collections;
// Needed in Unity 5+
using UnityEngine.SceneManagement;

public class SceneManagementExamples : MonoBehaviour
{
    // Name of new scene. Don't forget to add to build settings!
    public string scene;

    // Load the new scene
    public void LoadScene(string newScene)
    {
        SceneManager.LoadScene(newScene);
    }

    // Reload the current scene
    public void ReloadScene()
    {
        SceneManager.LoadScene(SceneManager.GetActiveScene().buildIndex);
    }
}

UIExamples.cs

// Various UI examples for Unity 5+
using UnityEngine;
using System.Collections;
// Needed fro UI in Unity 5+
using UnityEngine.UI;

public class UIExamples : MonoBehaviour
{
    // Set the target UI Text in the Inspector
    public Text uiText;

    // Set the target UI image in Inspector. UI Image must be "filled" type
    public Image uiImage;

    private int uiNumber = 7;

    void Update()
    {
        if (Input.GetButtonDown("Jump"))
        {
            // Basic usage
            uiText.text = "HELLO";

            // Fill amount is in a range from 0-1. Empty
            uiImage.fillAmount = 0;
        }
        else if (Input.GetButtonDown("Fire1"))
        {
            // Numbers must be converted to strings
            uiText.text = uiNumber.ToString();
            
            // Larger ranges of number can be converted by dividing with the max value. Halfway
            uiImage.fillAmount = 3.5f/uiNumber;
        }
        else if (Input.GetButtonDown("Fire2"))
        {
            // Numbers can be formatted to display a certain number of places
            uiText.text = uiNumber.ToString("000");

            // Full
            uiImage.fillAmount = 1;
        }
    }
}