NullReferenceException: Object reference not set to an instance of an object
CombatBehavior.FixedUpdate () (at Assets/Scripts/CombatBehavior.cs:92)
NullReferenceException: Object reference not set to an instance of an object
CombatBehavior.FixedUpdate () (at Assets/Scripts/CombatBehavior.cs:94)
gameObject.GetComponent<DamageDeal>().DealDmg();
gameObject.GetComponent<DamageDealToSkeleton>().DealDmgToSkeleton();
Hello, im having troubles with NullRefrence Exception. Could anyone explain me what am i doing wrong. As a disclaimer i want to tell that two lines there were working but i wanted to improve some of my code, so i ended up ctrl + z-ing everything what did a mess. But unfortunetly its gone... Unity still telling me that there is Null value.
I was trying to solve it by setting something like this:
GameObject player = GameObject.Find("Player");
DamageDeal damageDeal = player.GetComponent<DamageDeal>();
damageDeal.DealDmg();
DamageDealToSkeleton damageDealToSkelet = player.GetComponent<DamageDealToSkeleton>();
damageDealToSkelet.DealDmgToSkeleton();
in my Game Object Player -> CombatBehaviour.cs -> FixedUpdate.
It's a matter of life and death, please.
Are you sure the scripts are still on the object after you did the ctrl+z deal?
Is everything correctly spelled? Case-sensitive.
With what you have presented i feel like this is the only thing we have to go by.
Triple check it all :)
Related
I have an ai spawner BP and inside I want to call an event by timer to increase the characters walk speed after 10s, however the cast always fails. I have tried casting to the enemy and also tried to make an enemy ref object variable but still no luck. Any idea why I cant get it?
GetPlayerCharacter returns the current "Player Character" Object; this is the object the player's PlayerController is controlling, not an spawned AI Zombie.
The cast fails because the object going in is not of the type you are trying to cast it to.
Casting doesn't "Get" you an object that you cast to. It can refine the code context for an item that is of that type already.
If you want to get a reference to the zombie to change its walk speed, you need to hold onto a reference of it after spawning to run it into this code.
Is there some way in Swift that I can tell when an SKSpriteNode has actually been removed from the scene? I don't think it's actually done when removeFromParent is called, but instead I think it's done later, when Sprite-Kit thinks it's convenient to do so.
I'm trying to understand the full life cycle and I've noticed that a sprite can still be involved in contact and collisions in didBeginContact even after that sprite has been removed.
If I print out the contents of children (i.e. the array holding all the children of the scene) I see that the sprite is removed as soon as removeFromParent called, but the sprite is still available (at least, for this execution of the SK game loop).
Edit: This question came out from an earlier question of mine concerning didBeginContact being called multiple times for one contact (Sprite-Kit registering multiple collisions for single contact) and discovering that removing the sprite during the first contact did not prevent the subsequent contact(s). (Because SK has 'queued' to contacts in advance.) so I was wondering when the sprite is actually removed.
Am I missing the obvious? So even after removeFromParent the sprite is still around. However, it might well be because I have assigned the node to a temporary SKSpriteNode variable, then as long as that variable is around, there is a strong reference to the node, so it won't be deallocated. Also the SKPhysicsContact object itself will retain a reference to the physicsBody, which has a reference to the node which I think will also prevent allocation.
Update
To see when a sprite is actually released, use the deinit() method:
deinit {
print("Invader of type \(type) deinitialised")
}
I think this can only be added in a subclass definition, not via an extension.
Having a variable with a strong reference to the node being removed will prevent the node from being de-allocated until that variable is itself removed or changed to refer to something else.
If I've understand your question, I think it's not needed because you can always do:
if let myNode = self.childNode(withName: "//myNode") {
// ok myNode exist
}
Hope it helps you, you can write this code wherever you think is necessary.
Update:
About the reformulation of your question take a look below to these comments.
I have a suggestion after reading through the comments... move the node to a place outside of the playable area of your game, then remove it from parent. At this point you don't have to worry about when the physics body gets removed or when SK handles it. Or you could set the physicsBody? to nil at the same time, or use a bitmask flag as KoD suggested.
You can override all of the functions in the SK loop and check to see exactly when your pb is removed: https://developer.apple.com/library/content/documentation/GraphicsAnimation/Conceptual/SpriteKit_PG/Actions/Actions.html
Now I am facing a ghost object.
There was a script attached to an object which I deleted. But for some reason, the script's update function is always being called.
I added this line to the Update: Debug.Log(name), and its name is Flamestrike, but when I search it in the hierarchy, there are no results.
And if I set its position to 0,1,0 (so it should be visible), it is not visible in the game either.
So please help me because it drives me crazy :(
Edit:
Debug.Log("a");
if(transform.parent == null) {
transform.SetParent(GameObject.Find("Canvas").transform);
Debug.Log("Canvas");
}
I also tried this, and it prints Canvas, so it sets its parent to Canvas, but I can't see any Flamestrike objects under Canvas.
When Instantiating a prefab GameObject, for some reason it was being created with Hidden Flags. In order to solve this, we added the code: this.gameObject.hideFlag = HideFlags.None; which allowed the object to show up in the hiearchy finally.
The only other source I could find on this was this answer, which had basically no explanation as to why it occured. http://answers.unity3d.com/questions/921819/instantiated-prefabs-not-showing-up-in-hierarchy.html (quoted below)
Found the issue, not sure why but: These two ways are working (prefab
is a GameObject defined elsewhere).
Player1 = Instantiate(prefab) as GameObject;
Instantiate(prefab) as GameObject;
For some reason the prototype:
Instantiate(prefabName, position, rotation);
Was not working.
(Sorry if this is not the correct way to write this, but the comments are too short, and can't be formatted)
This not fully true, I think.
This hidden gameObject wasn't created via script. I dragged the prefab to the scene, then somehow I didn't delete the prefab fully. (or didn't even delete, just made it hidden)
It disappeared in the hieararchy, but it wasn't deleted fully.
After we made the object visible via script, now it is visible.
(but only in play mode, so I can't delete it, because it is not visible in scene view)
And it got some interesting components/attributes.
The original story:
FlameStrike - a Container for scaling purposes (empty gameObject)
-FlameStrike - a gameobject with animation, FlameStrike.cs script etc.
--Particle System - a part. system with this exact name.
But after we found the remaining hidden object it was like this:
So I don't understand what I did. It deleted some parts of the prefab, but also mixed some parts,
(like adding the Particle System object's Particle System component to this FlameStrike object)
then made it hidden. Is there a hotkey for this? :D Because it is not script related issue, I did this in the editor.
I have a scene called Level1, which takes the hero and the enemy from a layer called GameLayer. I heard that an efficient way of doing this is using tags and retrieving it using getChildByTag. I tried this out, but I'm having many issues. I'm using SneakyInput. On Level1, there is a leftJoystick (for enemy movement), and a rightJoystick (for firing projectiles). I have an addEnemy and addHero method in my GameLayer, which I call. Everything I've mentioned works.
In my Level1 scene I have a method called moveHero (which obviously is supposed to move the hero with the joystick.). Through basic debugging I know the problem is the geteChildByTag line. I test out the hero's position through NSLog, and it's saying 0,0. Which is weird because on screen you can see the hero. But I also realized I'm calling the addHero method without using getChildByTag.
I hope I'm being clear here. I've uploaded GameLayer.h and GameLayer.m onto 4shared. http://www.4shared.com/file/PqhjoMFy/GameLayer.html
Hopefully you can take a look at it and point me in the right direction.
BTW: There are no errors or crashes. It's just not working.
Thanks in advance.
getChildByTag will never crash, it's a pretty nicely coded method that just loops through the children array of the object and checks to see if any objects match, that way you don't get assertion issues.
You have some serious issues here with your code.
Firstly..
GameLayer *heroInstance = [[GameLayer alloc] init];
CCSprite *hero = (CCSprite *)[heroInstance getChildByTag:1];
NSLog(#"Hero position X: %f", hero.position.x);
NSLog(#"Hero position Y: %f", hero.position.y);
This will never work, heroInstance is a brand new object, it has no children, also you've just created a memory leak here.
Your hero is a child of the spritesheet, which is a child of the scene.
To reference your child you must call getChildByTag on your spritesheet (which you probably need to reference by calling getChildByTag on your scene..
something like this.
[[self getChildByTag:spritesheet] getChildByTag:hero];
Also, use an enum, so that you don't have to remember what numbers certain tags are (look at the cocos2d example projects).
I am working on a game. There are balls that fall from the top of the screen, and the player has to catch them, as the are caught they stack ontop of one another. I have a method that creates each new ball and adds it to an Array that i use to move the sprites. Problem is that the after they collide I need them to stop moving, since the array is called on to move them they all move. And if i try to make them stop they all stop. So I was hoping to create a pointer attribute if ther is such a think, for example "sprite.position" I need a new attribute that i can check like a boolean. I was hoping to create a attribute like sprite.hasCollided and if it returns YES then the ball should no longer move. Is this possible or is there a better way to do it?
Thanks
Tanner
I would suggest you create a ball object. And add the boolean as as part of the object.
CCNodes (and, by inheritence, CCSprites) have a userData property, which is a void*. You can use this to relate a custom object to a cocos2d object. Keep in mind if you use the userData option, you will, in most cases, need to allocate any memory when you create/assign the sprite, and release it when you are done.
int* myInt = (int*)malloc(sizeof(int));
*myInt = 0;
sprite.userData = myInt;
//some time later, when you are done with the sprite
free(sprite.userData);
As an improvement on the userData property, you can do what xuanweng suggests and create a ball object containing various game-related properties for the balls, and assign an instance of this to each of your ball CCSprites using the method above.