Other sources have suggested overriding the isItemValid method of IItemHandler to check if an item can be placed in a slot (e.g., only allow smeltable items in a furnace). I don't see this method available in documentation

 

Should I be performing this check inside an overridden insertItem method instead?

 

Thanks! brand new to modding so bear with me

I believe that isItemValid is a method in Slot. I have a custom inventory slot that extends the Slot class, and that's where I control which items can be placed in certain slots. Not sure if this is what you're looking for.

3 hours ago, cptcorndog said:

Other sources have suggested overriding the isItemValid method of IItemHandler to check if an item can be placed in a slot (e.g., only allow smeltable items in a furnace). I don't see this method available in documentation

 

Should I be performing this check inside an overridden insertItem method instead?

 

Thanks! brand new to modding so bear with me

You should make a custom ItemStackHandler that extends ItemStackHandler in which you overwrite insertItem and extractItem, and check if the itemstack is valid. I have a small example of what I mean here:

    protected boolean canInsert(ItemStack stack, int slot) {
        return true;
    }

    protected boolean canExtract(ItemStack stack, int slot, int amount) {
        return true;
    }

    @Override
    public boolean isItemValid(int slot, @Nonnull ItemStack stack) {
        return this.canInsert(stack, slot);
    }

    @Nonnull
    @Override
    public ItemStack insertItem(int slot, @Nonnull ItemStack stack, boolean simulate) {
        if (this.canInsert(stack, slot)) {
            return super.insertItem(slot, stack, simulate);
        } else {
            return stack;
        }
    }

    @Nonnull
    @Override
    public ItemStack extractItem(int slot, int amount, boolean simulate) {
        if (this.canExtract(this.getStackInSlot(slot), slot, amount)) {
            return super.extractItem(slot, amount, simulate);
        } else {
            return ItemStack.EMPTY;
        }
    }

But this isn't necessarily needed, as you should be able to modify isItemValid when instantiating the ItemStackHandler:

    public final ItemStackHandler inv = new ItemStackHandler(1) {
        @Override
        public boolean isItemValid(int slot, @Nonnull ItemStack stack) {
            return super.isItemValid(slot, stack); //check stack.
        }
    };

Also, make sure you are exposing the ItemHandler capability, or your inventory will not work properly.

47 minutes ago, unassigned said:

You should make a custom ItemStackHandler that extends ItemStackHandler in which you overwrite insertItem and extractItem, and check if the itemstack is valid. I have a small example of what I mean here:

But this isn't necessarily needed, as you should be able to modify isItemValid when instantiating the ItemStackHandler:

    public final ItemStackHandler inv = new ItemStackHandler(1) {
        @Override
        public boolean isItemValid(int slot, @Nonnull ItemStack stack) {
            return super.isItemValid(slot, stack); //check stack.
        }
    };

Also, make sure you are exposing the ItemHandler capability, or your inventory will not work properly.

 

The latter is what I'm trying to accomplish but Eclipse is raising an error when I try to override this method, and when I search through ItemStackHandler and IItemHandler I don't see this method declaration...

Careful with ItemHandlerSubclasses that override insertion/extraction behavior. Sometimes you want your machine to be able to insert things and not external forces, such as the player or hoppers. If you use a subclass that prevents insertion categorically, you can't add items to it even when you want to.

 

For such things I use a wrapper that I expose with GetCapability and have an internal regular handler that works as standard:

 

https://github.com/Draco18s/ReasonableRealism/blob/master/src/main/java/com/draco18s/hardlib/api/internal/inventory/OutputItemStackHandler.java

 

Note that all interaction is either passed to the internal wrapped handler or special logic is applied. This allows a machine to insert items into its own output slot, but nothing else can.