1.I have a class in which I have a method called ProjectileMotion() with return type IEnumerator and this method is being called from Start().
2. The above script is attached to a prefab that is instantiated from another class.
Problem:
In IENumerator ProjectileMotion() method, I need to have updated position of an object which is moving continuously,so I declared
//assigned the o=gameobject to it and it is moving continuously
Public Transform Target;
In ProjectileMotion(), if I do Target.transform,position, it gives the starting position only and not where it was at the time of instantiation of the prefab to which this script is attached, However, I am able to get the updated position of Target in Update method(checked using Debug.Log).
But I can not call the ProjectileMotion() in Update method of course, what should I do to get updated position of Target every time the prefab is instantiated and so the script is called.
Simply put ...
If you want the code to execute when the component is "started" then call it on start.
OR
If you want the code to execute each frame after the component has started then call it on update.
Judging by the name of this method I would think this is something that updates the position of a projectile after a gun has instantiated it.
The position being updated is likely a per frame operation so.
I would put this in the update method.
EDIT:
UNLESS ...
Does this function do a multiframe animation?
Unity has the concept of coroutines that allow to do certain actions of several frames. in this case you might be better off doing something like this in your start method ...
StartCoroutine(ProjectileMotion)
Related
I have a system that does initialization logic in Awake() and has an appropriate [DefaultExecutionOrder(-100)] attribute to guarantee its Awake() be called before each other "playable" game objects Awake(). Now I need the reverse logic, i need to call a function after each game object being destroyed.
I tried to traverse over root objects in main component's OnDestroy(), check if there's an object that is still alive (i.e. cast to bool gives true), and "pass the baton" of deinitialization to it (adding a CleanUp component on it). Then when this object's OnDestroy() is called it does the same logic, checks if there is at least one object alive, etc... The problem is that it doesn't work as i expected.
Also tried to make OnDestroy() async and check if there's no alive objects in the scene and wait for 100ms in a loop. The result is that playmode exits but the loop still goes on valid objects outside the playmode
Another approach was to instantiate an object with cleanup component in main component's OnDestroy() but Unity does not allow to instantiate in OnDestroy() event
Also tried to implement this logic in component's destructor but it was weirdly been called even before the Awake()
The other possible approach would be to use ISubsystem interface Unity provides but there's no clear documentation on how to use it.
I don't want to use any kind of "global factories" to instantiate and control objects
A possible way to workaround is to use other components' dependent logic in OnApplicationQuit() instead of OnDestroy() but it is the most fallback solution for me
What is the best way for component to be initialized before each other and outlive everyone?
I'm attempting to dynamically add Manipulation Events to a ManipulationHandler that is being added to child objects of a parent. The parent object will be what the user is inspecting, but the user will be able to grab parts off of the parent and inspect them more closely. (i.e. you can look at an engine (parent object), but if you want to inspect the pistons (child objects) you can grab them and look at them)
Instead of having to go into every child object and manually add it in Unity I'd like to be able to add the parent object and just procedurally add the ManipulationHandler and ManipulationEvents on start or awake.
So far I have the following code for adding the ManipulationHandler script, but to add the ManipulationEvent I'm not sure how to set up the pointers so I can use the script and function I want from the source:
gameObject.AddComponent<ManipulationHandler>();
ManipulationHandler handler = gameObject.GetComponent<ManipulationHandler>();
ManipulationEvent newevent = new ManipulationEvent();
ManipulationEventData eventdata = new ManipulationEventData();
eventdata.ManipulationSource = gameObject;
The program works when I grab the objects, but I'd like to add manipulation events when I grab them so I can display additional data.
I see there's a getter and setter for Pointer in ManipulationEventData, but I'm not sure how to instantiate IMixedRealityPointer and how to get it to work. I'm also not sure if that's the object I actually need to accomplish what I'd like to accomplish.
I apologize in advance if I've missed something obvious. I'm new to MRTK.
Thanks!
The ManipulationHandler has four callback events among them OnManipulationStarted and OnManipulationEnded you can simply add listeners to. (see UnityEvent.AddListener)
Unless I understood your question wrong you don't have to instantiate any IMixedRealityPointer. You don't create the event data yourself but rather the ManipulationHandler feeds these events with the current event data including the interacting pointer information. The ManipulationHandler uses OnPointerDown and OnPointerDragged and OnPointerUp via the IMixedRealityPointerHandler interface in order to manage the interacting pointers and invokes the according events where needed.
Instead of using AddComponent followed by GetComponent directly store and use the return value of AddComponent which will be the reference of the newly added Component. MRTK also has an extension method
T EnsureComponent<T>(this Component component) where T : Component
so that you can simply use e.g.
var handler = this.EnsureComponent<ManipulationHandler>();
which internally first checks whether the component already exists, and if not it adds it.
Note that in order to enable near interactions you will also need a NearInteractionGrabbable so you should add this one too.
You also will have to make sure that your objects have some sort of Collider attached to the same GameObject as the NearInteractionGrabbable.
...
gameObject.transform.EnsureComponnet<NearInteractionGrabbable>();
var handler = gameObject.transform.EnsureComponnet<ManipulationHandler>();
handler.OnManipulationStarted.AddListener(HandleOnManipulationStarted);
handler.OnManipulationEnded.AddListener(HandleOnManipulationEnded);
...
/// <summary>
/// If you need it later you need to store the pointer since unfortunately in
/// OnManipulationEnded the <see cref="ManipulationEventData.Pointer"/> is null
/// (no idea why they do it this way :D )
/// </summary>
private IMixedRealityPointer _pointer;
private void HandleOnManipulationStarted(ManipulationEventData eventData)
{
_pointer = eventData.Pointer;
// whatever shall happen when manipulation started
}
private void HandleOnManipulationEnded(ManipulationEventData eventData)
{
// whatever shall happen when manipulation ended
}
Note: I am not sure if this thing you are trying to achieve is possible with this architecture ... it is very possible that nesting various ManipulationHanlder leads to strange behavior here and there. Especially very small parts will be almost impossible to grab ...
I have instantiated a prefab in the scene that gets destroyed after 2 secs. I want to change its speed variable in its move script so that whenever it instantiate it has new speed.
The instantiate function returns the game object you created.
GameObject prefabObject = Instantiate(...);
Then you can obviously do something like
prefabObject.GetComponent<moveScript>().speed = 4;
You have not provided enough information, but I will try to answer.
Will this be done by another script or the Move script you have attached on the prefab?
If from the Move script then:
private void Awake()
{
speed = MY_NEW_SPEED;
}
If from another script, then you first need to access the instantiated object and then its Move scripts. You have not provided enough information so I will assume you already have a reference to your instantiated object:
instantiatedObject.GetComponent<Move>().speed = MY_NEW_SPEED;
https://docs.unity3d.com/ScriptReference/GameObject.GetComponent.html
I have been trying to use SetActive () to turn on and off GameObjects.
I couldn't figure it out and ended up using:
GameObject.Find ("ObjectName").GetComponent<Image> ().enabled = false;
to turn off an image.
I am not trying to use the same script to turn off a GameObject that has multiple animations nested inside it.
GameObject.Find ("ObjectName").GetComponent<???> ().enabled = false;
GameObject.Find ("ObjectName").SetActive (false);
I am not sure what goes in the <>, but I have read I can do it with SetActive (), but that doesn't seem to work and gives me an "Object Reference not set to object" error.
So what is the difference between these two and how would I use them properly?
Using GetComponent allows you to enable/disable and interact with specific components on a GameObject.
For example, you may need to disable a GameObject's rigidbody at some point, but you still want that object, and everything else on it to be active. So you could simply say:
GameObject.Find("MyObject").GetComponent<Rigidbody>().enabled = false;
Note that what goes inside the "<>" is the class name of the component you want to interact with.
For example, if you had a script you have written yourself on a gameobject called MyScript, you could grab hold of it like so:
MyScript script = GamesObject.Find("MyObject").GetComponent<MyScript>().enabled = true;
Additionally, another good use of GetComponent is reading information from a script on an object.
For example, if you had a script called Health with a public variable HitPoints on an object, another script could gain access to that information using GetComponent.
if( enemyGameObject.GetComponent<Health>().HitPoints < 0 )
{
enemyGameObject.SetActive(false);
}
Using SetActive will enable and disable a GameObject entirely. This is less expensive than deleting / making a new object, and is thus often used in techniques like Object Pooling.
For example, if you had a GameObject that you needed disabled, but you knew you were going to need it again soon, it is far less expensive to just call
MyGameObject.SetActive(false);
...
MyGameObject.SetActive(true);
Than it is to delete that object entirely, and then make a new one when you are ready for it again.
To add up to the other answers, when a component is disabled it means the MonoBehaviour callbacks are not called anymore. So no Update, FixedUpdate, OnCollisionXXX and so on.
Awake is called when the object is created so it is obviously enabled by default at that stage. Start is called on the first run after Awake. So if you set the component off in Awake, Start will wait until you set it back on from elsewhere.
OnEnable/OnDisable are called when you modify the enabled property.
SetActive works on the GO and is pretty much a shortcut to disable all components at once.
gameObject.SetActive(false);
foreach(var comp in GetComponentsInChildren<MonoBehaviour>()){
comp.enabled = false;
}
those are fairly similar in result (maybe not in efficiency). Actually, when you set a game object on/off, the OnEnable/OnDisable of each component is called. All MonoBehaviour callbacks are not called anymore if you set the object off.
So, the choice is dependent on what you are after, if you wish to disable movement but still see the object and other actions:
GetComponent<Movement>().enabled = false;
if you wish to kill an enemy:
enemy.gameObject.SetActive(false);
Note that even though a component is disable, does not mean you cannot interact with it. You can still manually call any method on it. Consider this:
AnyComponent ac = gameObject.GetComponent<AnyComponent>();
ac.enabled = false;
ac.AnyMethod();
Valid and will do what it is meant to do considering it does not require an Update or a FixedUpdate (Physics action).
A deactivated component cannot be found with GetComponent, you can get it with GetComponentInChildren(true) since it also searches the game object and its children. I am not sure whether it returns the first found or the first active found.
myGameObject.SetActive(false);
AnyComponent ac = myGameObject.GetComponent();
AnyComponent acic = myGameObject.GetComponentInChildren(true);
even though the GO has a AnyComponent attached, ac is null, acic is not (seems to be a 5.3 feature though).
http://docs.unity3d.com/ScriptReference/Component.GetComponentInChildren.html
Finally, for a component to expose the tick, it needs to have a Start method in the script (don't ask why...).
Setting .enabled turns one component on a GameObject on or off, e.g. an Image. Using SetActive() turns the whole GameObject on or off.
Choosing which to use should correspond with what you want to disable.
I see that we can initialize Variable in Awake() or Start() and Awake() will be called before Start().
When should we initialize in Awake and Start to have the best performance?
Usually Awake() is used to initialize if certain values or script are dependent on each other and would cause errors if one of them is initialized too late (awake runs before the game starts).
Awake is also called only once for every script instance.
Let me quote the Documentation:
[...] Awake is called after all objects are initialized so you can safely speak to other objects or query them using eg. GameObject.FindWithTag. Each GameObject's Awake is called in a random order between objects. Because of this, you should use Awake to set up references between scripts, and use Start() to pass any information back and forth. Awake is always called before any Start functions. This allows you to order initialization of scripts. Awake can not act as a coroutine.
and about Start():
Start is called on the frame when a script is enabled just before any
of the Update methods is called the first time.
Like the Awake function, Start is called exactly once in the lifetime
of the script. However, Awake is called when the script object is
initialised, regardless of whether or not the script is enabled. Start
may not be called on the same frame as Awake if the script is not
enabled at initialisation time.
Where the last part makes one big difference
To get to your question:
If the script is NOT enabled at the beginning of your game, and you don't need the variables to be initialized, start would be saving performance as awake() would be called regardless...
every variable would be initialized at the very beginning. At least that's the logical assumption I make.
This topic is well described in the official docmentation (Awake and Start).
This section describes why you might need two functions:
The Awake function is called on all objects in the scene before any
object's Start function is called. This fact is useful in cases where
object A's initialisation code needs to rely on object B's already
being initialised; B's initialisation should be done in Awake while
A's should be done in Start.
The difference between Awake and Start is that Start is called only when a script is enabled.
These two functions are called before the first Update method and there is no performance difference between them. I would say that Awake is used to initialize all objects (like a constructor), and Start is used to link the objects or do something before a game starts.
Awake is the equivalent of the ctor. It is called when a MonoBehaviour is created, before any other method if the object is active.
Start is run the first time the MonoBehaviour is activated. This can be right after Awake or long after. This allows to perform actions that are related to the current state of the app or objects.
For instance, you create an enemy, in Awake, you place everything that is basic initialisation. Then, the enemy is deactivated at the end of Awake. Later on, the enemy is about to be activated but you want to make it red if player is having some specific weapon, then you do it in Start.
IMPORTANT: If a prefab is created and the game object is off by default in the prefab, the Awake is not called until set on. In the case of a pool creation where prefab may be off, the awake is happening first time the pooled object is activated.
OnEnable is similar to Start but happens on every SetActive(true) and on start if enabled. This can be a candidate for your enemy willing to change color over the level based on the player magna for instance.
There's not much difference in the performance. But I can tell you a difference between them.
Take a simple example. Say if you want to print "HELLO" in console even if you have not activated the script in inspector, using Awake() function, you can print it in the console. But if you had written the same thing in Start() function and the script wasn't activated, you don't get any output in the console. That's the difference.
Codes in Start() function get executed only if the script is activated while, codes in Awake() function get executed even if the script is not activated. Try it !
I'd claim there is no real performance difference at all.
What Minzkraut stated
If the script is NOT enabled at the beginning of your game, and you don't need the variables to be initialized, start would be saving performance as awake() would be called regardless...
every variable would be initialized at the very beginning. At least that's the logical assumption I make.
is only semi true. If you do everything only in Start the UX might be even worse since instead of one bigger lag when starting the app - which in my eyes is totally acceptable - it might lead to smaller but more lags during game play which I personally would avoid as much as possible.
In general it was already often explained in the other answers how and when Awake and Start are called and that basically it is "just" a timing difference.
For details refer to Execution Order of Events
Leaving disabled components and inactive GameObjects aside my personal thumb rule is
Use Awake for everything where you don't rely on any other component and references.
E.g. set default field values, populate things using GetComponent etc
Use Start for everything where you do rely on other components such as accessing the results of GetComponent
This way these other components supposedly did already receive their Awake call so they themselves are already linked up and ready to be used by others.
This solves timing and dependency issues in the most cases.
Where this is not enough you would start to tweak the Script execution order or use events.
And then there is another quite important difference in the use case of using Instantiate or AddComponent
Awake (and OnEnable except using Instantiate and the component is disabled) will be called right away during the instantiation and any code line after Instantiate will be executed after it is finished.
Start however will be delayed until the end of that frame (or until enabling if the component was disabled in Awake).
This allows you to have enough time to use Instantiate and modify some field values before Start is called and can now base its behavior on the modified field values.
For example this
public class Example : MonoBehaviour
{
private class X : MonoBehaviour
{
public int x = -1;
private void Awake()
{
Debug.Log($"Awake {x}");
x = 12;
}
private void OnEnable()
{
Debug.Log($"OnEnable {x}");
}
private void Start()
{
Debug.Log($"Start {x}");
}
}
private void Update()
{
if (Input.GetKeyDown(KeyCode.Space))
{
Debug.Log("Instantiate");
var x = gameObject.AddComponent<X>();
Debug.Log("After instantiate");
x.x = 42;
}
}
}
will produce the output
Instantiate
Awake -1
OnEnable 12
After Instantiate
Start 42