Table of Contents

• Execution Order of Event Functions
• Awake vs Start
• HideInInspector vs NonSerialized vs SerializeField
  • HideInInspector
  • SerializeField
• Serialization
• Don't define a Coroutine named Main
• SendMessage
• OnBecameVisible / OnBecameInvisible
• Object
  • Instantiate
  • Destroy
• GameObject
  • Create Empty with Code
  • FindWithTag
• Coroutine
• C# classes need to have its own script with the class' name?

Execution Order of Event Functions discussion

Awake vs Start discussion

• Awake and Start are called only once in thier lifetime
• Awake is called when the script instance is being loaded(whther or not the script enabled)
• Start is called on the frame when a script is enabled(before Update)
• Awake is called on all objects in the scene before any object's Start is called.

HideInInspector vs NonSerialized vs SerializeField discussion

• Things can only be visible in the inspector if they are serialized.
• If something is not serialized it will never show up in the inspector.
• HideInInspector attribute make it invisible in the inspector but still allow each instance of a SerializeField to hold its own default value.

HideInInspector

public class ExampleClass : MonoBehaviour {
    [HideInInspector]
    public int p = 5;
}

SerializeField

public class SomePerson : MonoBehaviour
{
    //This field gets serialized because it is public.
    public string name = "John";

    //This field does not get serialized because it is private.
    private int age = 40;

    //This field gets serialized even though it is private
    //because it has the SerializeField attribute applied.
    [SerializeField]
    private bool hasHealthPotion = true;
}

Serialization discussion

Many of unity features build ontop of the serialization system:

• Storing data stored in your scripts
• Inspector window
• Prefabs
• Instantiation
• Saving and loading scenes
• Hot reloading of editor code
• Resource.GarbageCollectSharedAssets()

[Serializable]
class Animal
{
    public string name;
}

class MyScript : MonoBehaviour
{
    public Animal[] animals;
}

Don't define a Coroutine named Main discussion

Don't define a coroutine named Main.

I wrote a coroutine named Main. It executed twice, in an unexpected way.

I've tweaked many times to understand why. Main executed even I didn't explicitly call StartCoroutine.

At last, I renamed Main to Main2, and it worked all the way I expected.

SendMessage reference

• Calls the method named methodName on every MonoBehaviour in the GameObject.
• It's not possible to get a return value from SendMessage or BroadcastMessage

OnBecameVisible / OnBecameInvisible reference

• When running in the editor, scene view cameras will also cause this function to be called
• OnBecameInvisible is only called the object had been visible

Object reference

Instantiate

• If cloning a Component then the GameObject it is attached to will also be cloned
• All child objects and components will also be cloned

// Preferred
public static T Instantiate(T original);
public static T Instantiate(T original, Transform parent);
public static T Instantiate(T original, Transform parent, bool worldPositionStays);
public static T Instantiate(T original, Vector3 position, Quaternion rotation);
public static T Instantiate(T original, Vector3 position, Quaternion rotation, Transform parent);

// 'as T' required for type
public static Object Instantiate(Object original);
public static Object Instantiate(Object original, Transform parent);
public static Object Instantiate(Object original, Transform parent, bool instantiateInWorldSpace);
public static Object Instantiate(Object original, Vector3 position, Quaternion rotation);
public static Object Instantiate(Object original, Vector3 position, Quaternion rotation, Transform parent);

Instantiated GameObject

1. Before Instantiate
2. Awake of Instantiated GameObject
3. After Instantiate
4. Start of Instantiated GameObject

Destroy

• If obj is a Component it will remove the component from the GameObject and destroy it.
• Actual object destruction is always delayed until after the current Update loop, but will always be done before rendering.

public static void Destroy(Object obj, float t = 0.0F);

GameObject reference

Create Empty with Code

• Transform is always added to the GameObject that is being created.

GameObject player;
player = new GameObject("Player");
player.AddComponent<Rigidbody>();
player.AddComponent<BoxCollider>();

FindWithTag

respawn = GameObject.FindWithTag("Respawn");

Coroutine reference

• Coroutines have virtually no performance overhead.
• StartCoroutine function always returns immediately,
• yield return <something> to make coroutine resume after <something>
• yield break to stop the coroutine
• SEE: Execution Order

C# classes need to have its own script with the class' name? discussion

• Only MonoBehavior, ScriptableObject, and the children of either MUST have their own files
• Unity magic (adding classes as Components, etc..) requires the class be alone in a file, with the same name.