#NullReferenceException: Object reference

1 messages · Page 1 of 1 (latest)

coral comet
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making a thread for this

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it's impossible to say from the exception alone

wispy dagger
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alright

coral comet
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myContainer could be null. myContainer.icon could be null. item could be null

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myContainer probably isn't null because you just instantiate a prefab

wispy dagger
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yeah

coral comet
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Did you assign icon in the prefab?

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not just on a random instance of the prefab

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on the actual prefab

wispy dagger
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in my assets

coral comet
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if you double click the prefab asset, it will open in isolation, and you can look at it there

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or just click on the asset, since icon will appear in the inspector

wispy dagger
wispy dagger
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so do i set an image for the slot?

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as default

coral comet
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Image is the component that displays a sprite

wispy dagger
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ik

coral comet
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And yes, you absolutely have to have one assigned

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if icon is null, that code will always throw an NRE

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The item container should come with its own Image component

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Your code is trying to set the sprite for that image

wispy dagger
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everything gives me a type mismatch

coral comet
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You're trying to drag a scene object into the prefab.

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You can't do that.

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This prefab is supposed to be a thing that can display a single item's sprite, correct?

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If not, explain how this is supposed to work.

wispy dagger
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yes it shows a single items sprite

coral comet
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okay, so each item container needs its own Image

wispy dagger
coral comet
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what are you attempting to drag in, then?

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it would not make sense to reference an Image on another prefab

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you need to add an Image to the item container prefab

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Weren't you originally trying to retrieve an Image from a game object named "icon" on the prefab?

coral comet
wispy dagger
coral comet
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scriptable objects don't have transforms

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i don't understand

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myContainer.icon.sprite = item.icon;

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Do you mean this line?

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I was talking about your original code from earlier.

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var itemIcon = obj.transform.Find("icon").GetComponent<Image>();

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This bit.

wispy dagger
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oh

coral comet
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There is room for confusion because you've named two things "icon"

wispy dagger
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here

coral comet
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You should rename the item container's field

wispy dagger
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`public class ItemData : ScriptableObject
{
public string id;
public string displayName;
public Sprite icon;
public GameObject prefab;
public bool stackable = true;
public ItemType type;

public enum ItemType
{
    weapon,
    tool,
    material,
    consumable,

}

}`

wispy dagger
coral comet
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I'd just call it image or iconDisplay

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Giving different things (especially things you use together) the same name is a recipe for confusion

wispy dagger
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i changed it

coral comet
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you might need to re-assign the reference on the prefab now

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since the old icon fields is gone

wispy dagger
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yeah

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wha now i cant put it in

wispy dagger
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i still get the same error tho

coral comet
wispy dagger
coral comet
wispy dagger
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i thought thats what was supposed to be null

coral comet
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The Image component will not yet have a sprite assigned to it

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so the sprite can be null

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but if containerIcon is null, you will get an error when you try to use it.

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myContainer.icon.sprite <--- null reference exception immediately occurs

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You must drag that Image component into the containerIcon field

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so that, after you instantiate the prefab, you can set the sprite of the Image

wispy dagger
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sorry my wifi decided to commit suicide

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anyways i fixed a little up

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i realized that itemPrefab should not have been on the inventory slot prefab cause thats the container, instead i put it on an item prefab

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which sorta i suppose reveals the purpose of the name

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i dont get an error anymore

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but it do some funky stuff

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it instantiates the prefab, but not actually in the inventory slot, it also randomly creates 45 of them

coral comet
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I thought you wanted to show each item in an item container.

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So is there supposed to be just one item container, then?

wispy dagger
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each item would have their own, or it could be empty

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dynamic inventory

coral comet
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an item would have an item container?

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or do you mean that each item would be in a separate item container?

wispy dagger
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yeah like their own inventory slot

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in games like...

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terraria, minecraft, etc

coral comet
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sounds like you want to instantiate all of the item containers ahead of time and keep them in a list, then

wispy dagger
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yeah

coral comet
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so you'd have a List<ItemContainer>

wispy dagger
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i have items addable and removable from the inventory item list

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public List<ItemData> itemsInInventory = new List<ItemData>();

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item data is the scriptable object

coral comet
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yes, but I'm talking about the actual containers you display your items in

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if you're going to create them in advance (maybe making 9 of them for a minecraft-style item bar), you need to keep track of them

wispy dagger
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hotbar

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all the slots are already in the game

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so technically nothing should be instantiated container wise

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i need to instantiate the item icon into the slots

coral comet
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you don't need to instantiate anything

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you just need to assign the icon

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I'm having some trouble figuring out your design here

wispy dagger
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so make a child object of the slot that has a component image

coral comet
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you already have that, don't you?

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you already have an Image

wispy dagger
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then have the item icon in that slot be what that is

wispy dagger
coral comet
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assign the item's icon into the sprite field of that Image component

wispy dagger
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for reference to you

screenies.png
wispy dagger
coral comet
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if you have a list of item containers, you can do containers[0].containerIcon.sprite = item.icon; to make the first container display whatever item.icon is

wispy dagger
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i think im gonna come back to this tommorow, ive been working on this for too long and my cranium needs a break

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i basically ask you for help on a daily basis

coral comet
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inventory systems require a solid design

wispy dagger
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yeah

coral comet
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I spent quite a while implementing one for a soulslike game

wispy dagger
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i left cause i mostly had school work

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i think i need some kind of array for my inventory slots

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then when adding it'll check if each slot is filled or not

coral comet
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Yes, you should do that.

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I thought you were creating and destroying the slots

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since you were instantiating itemContainer as you iterated over your items

wispy dagger
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yeah that's why i changed it to create the itemPrefab

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well the itemPrefab sprite is whatever the item data's icon is

wispy dagger
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public GameObject reference to each slot would be a lot

coral comet
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if they're all parented to a single object, you could just do GetComponentsInChildren<ItemContainer>() to grab them all

wispy dagger
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they're all parented to inventory slots object

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so all the slots are parented to an object