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--- tutorial:inventory [2019/08/06 15:31] – fudge
+++ tutorial:inventory [2025/03/30 22:06] (current) – [Storing items in a block as an Inventory] technici4n
@@ Line 1: / Line 1: @@
 ====== Storing items in a block as an Inventory ======
-The standard way to store items in a BlockEntity is to make it an ''Inventory''.
+Make sure you've [[tutorial:blockentity|made a block entity]] before reading this tutorial.
-This allows hoppers (or other mods) to insert and extract items from your BlockEntity without any extra work.
+The simplest way to store items in a BlockEntity is to make it an ''Inventory''. This allows hoppers (or other mods) to insert and extract items from your BlockEntity without any extra work. For more flexible and complex ways to store items, refer to the [[tutorial:transfer-api_item_storage|Item transfer with Storage<ItemVariant>]] tutorial.
+This tutorial is written for 1.21. For older versions, some methods may change.
 ===== Implementing Inventory =====
-''Inventory'' is just an interface, which means the actual ''ItemStack'' state will need to be stored on your ''BlockEntity''.
-A ''DefaultedList<ItemStack>'' can be used as an easy way to store  these ''ItemStacks'',
+''Inventory'' is just an interface, which means the actual ''ItemStack'' state will need to be stored on your ''BlockEntity''. A ''DefaultedList<ItemStack>'' can be used as an easy way to store  these ''ItemStacks'', as it can be set to default to ''ItemStack.Empty'', which is the proper way of saying that there is no item in a slot. Implementing ''Inventory'' is fairly simple, but is tedious and prone to error, so we'll use a default implementation of it which only requires giving it a ''DefaultList<ItemStack>'' (copy this as a new file):
-as it can be set to default to ''ItemStack.Empty'', which is the proper way of saying that there is no item in a slot.
-Implementing ''Inventory'' is fairly simple, but is tedious and prone to error,
-so we'll use a default implementation of it which only requires giving it a ''DefaultList<ItemStack>'' (copy this as a new file):
 <code java ImplementedInventory.java>
 /**
  * A simple {@code Inventory} implementation with only default methods + an item list getter.
  *
- * Originally by Juuz
+ * @author Juuz
  */
 public interface ImplementedInventory extends Inventory {
     /**
-     * Gets the item list of this inventory.
+     * Retrieves the item list of this inventory.
      * Must return the same instance every time it's called.
      */
     DefaultedList<ItemStack> getItems();
-    // Creation
     /**
      * Creates an inventory from the item list.
@@ Line 27: / Line 30: @@
         return () -> items;
     }
     /**
-     * Creates a new inventory with the size.
+     * Creates a new inventory with the specified size.
      */
     static ImplementedInventory ofSize(int size) {
         return of(DefaultedList.ofSize(size, ItemStack.EMPTY));
     }
-    // Inventory
     /**
      * Returns the inventory size.
      */
     @Override
-    default int getInvSize() {
+    default int size() {
         return getItems().size();
     }
     /**
-     * @return true if this inventory has only empty stacks, false otherwise
+     * Checks if the inventory is empty.
+     * @return true if this inventory has only empty stacks, false otherwise.
      */
     @Override
-    default boolean isInvEmpty() {
+    default boolean isEmpty() {
-        for (int i = 0; i < getInvSize(); i++) {
+        for (int i = 0; i < size(); i++) {
-            ItemStack stack = getInvStack(i);
+            ItemStack stack = getStack(i);
             if (!stack.isEmpty()) {
                 return false;
@@ Line 54: / Line 60: @@
         return true;
     }
     /**
-     * Gets the item in the slot.
+     * Retrieves the item in the slot.
      */
     @Override
-    default ItemStack getInvStack(int slot) {
+    default ItemStack getStack(int slot) {
         return getItems().get(slot);
     }
     /**
-     * Takes a stack of the size from the slot.
+     * Removes items from an inventory slot.
-     * <p>(default implementation) If there are less items in the slot than what are requested,
+     * @param slot  The slot to remove from.
-     * takes all items in that slot.
+     * @param count How many items to remove. If there are less items in the slot than what are requested,
+     *              takes all items in that slot.
      */
     @Override
-    default ItemStack takeInvStack(int slot, int count) {
+    default ItemStack removeStack(int slot, int count) {
         ItemStack result = Inventories.splitStack(getItems(), slot, count);
         if (!result.isEmpty()) {
@@ Line 74: / Line 83: @@
         return result;
     }
     /**
-     * Removes the current stack in the {@code slot} and returns it.
+     * Removes all items from an inventory slot.
+     * @param slot The slot to remove from.
      */
     @Override
-    default ItemStack removeInvStack(int slot) {
+    default ItemStack removeStack(int slot) {
         return Inventories.removeStack(getItems(), slot);
     }
     /**
-     * Replaces the current stack in the {@code slot} with the provided stack.
+     * Replaces the current stack in an inventory slot with the provided stack.
-     * <p>If the stack is too big for this inventory ({@link Inventory#getInvMaxStackAmount()}),
+     * @param slot  The inventory slot of which to replace the itemstack.
-     * it gets resized to this inventory's maximum amount.
+     * @param stack The replacing itemstack. If the stack is too big for
+     *              this inventory ({@link Inventory#getMaxCountPerStack()}),
+     *              it gets resized to this inventory's maximum amount.
      */
     @Override
-    default void setInvStack(int slot, ItemStack stack) {
+    default void setStack(int slot, ItemStack stack) {
         getItems().set(slot, stack);
-        if (stack.getCount() > getInvMaxStackAmount()) {
+        if (stack.getCount() > stack.getMaxCount()) {
-            stack.setCount(getInvMaxStackAmount());
+            stack.setCount(stack.getMaxCount());
         }
     }
     /**
-     * Clears {@linkplain #getItems() the item list}}.
+     * Clears the inventory.
      */
     @Override
@@ Line 100: / Line 115: @@
         getItems().clear();
     }
+    /**
+     * Marks the state as dirty.
+     * Must be called after changes in the inventory, so that the game can properly save
+     * the inventory contents and notify neighboring blocks of inventory changes.
+     */
     @Override
     default void markDirty() {
         // Override if you want behavior.
     }
+    /**
+     * @return true if the player can use the inventory, false otherwise.
+     */
     @Override
-    default boolean canPlayerUseInv(PlayerEntity player) {
+    default boolean canPlayerUse(PlayerEntity player) {
         return true;
     }
 }
 </code>
-Now in your ''BlockEntity'' Implement ''ImplementedInventory'',
-and provide it with an instance of ''DefaultedList<ItemStack> items'' that stores the items.
+Now in your ''BlockEntity'', implement ''ImplementedInventory'', and provide it with an instance of ''DefaultedList<ItemStack> items'' that stores the items. For this example we'll store a maximum of 2 items in the inventory:
-For this example we'll store a maximum of 2 items in the inventory:
+<code java DemoBlockEntity.java>
-<code java>
 public class DemoBlockEntity extends BlockEntity implements ImplementedInventory {
     private final DefaultedList<ItemStack> items = DefaultedList.ofSize(2, ItemStack.EMPTY);
@@ Line 121: / Line 145: @@
         return items;
     }
-    ...
+    [...]
 }
 </code>
--->>>>>>>Remember markDirty() <<<<<<<<<--
+We're also gonna need to save the inventories to NBT and load it from there. ''Inventories'' has helper methods that make this very easy:
-We're also gonna need to save the inventories to tag and load it from there.
+<code java DemoBlockEntity.java>
-''Inventories'' has helper methods that makes this very easy:
-<code java>
 public class DemoBlockEntity extends BlockEntity implements ImplementedInventory {
-    ...
+    [...]
     @Override
-    public void fromTag(CompoundTag tag) {
+    public void readNbt(NbtCompound nbt, RegistryWrapper.WrapperLookup registryLookup) {
-        super.fromTag(tag);
+        super.readNbt(nbt, registryLookup);
-        Inventories.fromTag(tag,items);
+        Inventories.readNbt(nbt, items, registryLookup);
     }
     @Override
-    public CompoundTag toTag(CompoundTag tag) {
+    public NbtCompound writeNbt(NbtCompound nbt, RegistryWrapper.WrapperLookup registryLookup) {
-        Inventories.toTag(tag,items);
+        Inventories.writeNbt(nbt, items, registryLookup);
-        return super.toTag(tag);
+        return super.writeNbt(nbt, registryLookup);
     }
 }
 </code>
 ===== Extracting and inserting from your inventory =====
-Remember that the same thing can be done with any inventory...
+In our block class, we'll override the ''onUse'' behavior to insert and extract items from our inventory. Note that this can be done to any ''Inventory'' instance, not just our own (so you could do the same thing to a chest block, for example).
+First we'll handle inserting into the inventory. The player will insert the item he is holding if he is holding one. It'll go into the first slot if it is empty, or to the second slot if the first one is empty, or if the second is empty too we'll print some information about the inventory.
+Note that we call ''copy()'' when inserting the ''ItemStack'' into the inventory so it doesn't get destroyed alongside the player's ''ItemStack''.
+<code java DemoBlock.java>
+public class DemoBlock extends BlockWithEntity {
+    [...]
+    @Override
+    protected ItemActionResult onUseWithItem(ItemStack stack, BlockState state, World world, BlockPos pos, PlayerEntity player, Hand hand, BlockHitResult hit) {
+        if (world.isClient) return ActionResult.SUCCESS;
+        if (!(world.getBlockEntity(pos) instanceof DemoBlockEntity blockEntity)) {
+            return ItemActionResult.PASS_TO_DEFAULT_BLOCK_INTERACTION;
+        }
+        if (!player.getStackInHand(hand).isEmpty()) {
+            // Check what is the first open slot and put an item from the player's hand there
+            if (blockEntity.getStack(0).isEmpty()) {
+                // Put the stack the player is holding into the inventory
+                blockEntity.setStack(0, player.getStackInHand(hand).copy());
+                // Remove the stack from the player's hand
+                player.getStackInHand(hand).setCount(0);
+            } else if (blockEntity.getStack(1).isEmpty()) {
+                blockEntity.setStack(1, player.getStackInHand(hand).copy());
+                player.getStackInHand(hand).setCount(0);
+            } else {
+                // If the inventory is full we'll notify the player
+                player.sendMessage(Text.literal("The inventory is full! The first slot holds ")
+                    .append(blockEntity.getStack(0).getName())
+                    .append(" and the second slot holds ")
+                    .append(blockEntity.getStack(1).getName()));
+            }
+        }
+        return ItemActionResult.SUCCESS;
+    }
+}
+</code>
+We'll have the opposite behavior when the player is not holding an item. We'll take the item from the second slot, and then the first one if the second is empty.
+If the first is empty we pass it to default behavior.
+<code java DemoBlock.java>
+public class DemoBlock extends BlockWithEntity {
+    [...]
+    @Override
+    protected ItemActionResult onUseWithItem(ItemStack stack, BlockState state, World world, BlockPos pos, PlayerEntity player, Hand hand, BlockHitResult hit) {
+        ...
+        if (!player.getStackInHand(hand).isEmpty()) {
+            ...
+        } else {
+            // If the player is not holding anything we'll get give him the items in the block entity one by one
+            // Find the first slot that has an item and give it to the player
+            if (!blockEntity.getStack(1).isEmpty()) {
+                // Give the player the stack in the inventory
+                player.getInventory().offerOrDrop(blockEntity.getStack(1));
+                // Remove the stack from the inventory
+                blockEntity.removeStack(1);
+            } else if (!blockEntity.getStack(0).isEmpty()) {
+                player.getInventory().offerOrDrop(blockEntity.getStack(0));
+                blockEntity.removeStack(0);
+            } else {
+                return ItemActionResult.PASS_TO_DEFAULT_BLOCK_INTERACTION;
+            }
+        }
+        return ItemActionResult.SUCCESS;
+    }
+}
+</code>
+===== Implementing SidedInventory =====
+If you want to have different logic based on what side things (hopper or other mods) interact with your block you need to implement ''SidedInventory''. If say you wanted to make it so you cannot insert from the upper side of the block, you would do this:
+<code java DemoBlockEntity.java>
+public class DemoBlockEntity extends BlockEntity implements ImplementedInventory, SidedInventory {
+    [...]
+    @Override
+    public int[] getInvAvailableSlots(Direction side) {
+        // Just return an array of all slots
+        return IntStream.of(getItems().size()).toArray();
+    }
+    @Override
+    public boolean canInsert(int slot, ItemStack stack, Direction direction) {
+        return direction != Direction.UP;
+    }
+    @Override
+    public boolean canExtract(int slot, ItemStack stack, Direction direction) {
+        return true;
+    }
+}
+</code>