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====== Adding an Item ======

===== Introduction =====

Adding a basic item is one of the first steps in modding. You're going to need to create an ''<yarn class_1792>'' object, register it, and give it a texture. To add additional behavior to the item you will need a custom <yarn class_1792> class. In this tutorial and all future ones, the “''tutorial''” namespace is used as a placeholder. If you have a separate mod id, feel free to use it instead.

===== Create an Item instance =====

:!: If you're in version 1.21.2 or above, please directly read [[#Creating Items in 1.21.2+]].

First, create an instance of ''<yarn class_1792>''. The constructor takes in an ''<yarn class_1792>.<yarn class_1793>'' (or a ''FabricItemSettings'' unless versions since 1.20.5) instance, which is used to set item properties such as the durability, and stack count. For simplicity, we just do it in ''ExampleMod'' class, and store them in static fields.

<yarncode java [enable_line_numbers="true"]>
public class ExampleMod implements ModInitializer {

    // an instance of our new item
    // for versions below 1.20.4
    public static final class_1792 CUSTOM_ITEM = new class_1792(new FabricItemSettings());
    // for versions since 1.20.5, below 1.21.2
    public static final class_1792 CUSTOM_ITEM = new class_1792(new class_1792.class_1793());
    [...]
}
</yarncode>

===== Register the item =====

We've create a basic item, but it still does not exist in Minecraft, because it has not been registered. In Minecraft, almost everything has an registry, and items are no exceptions.

You'll use the vanilla registry system for registering new content. The basic syntax is ''<yarn class_2378>.<yarn method_10230>(Registry Type, <yarn class_2960>, Content)''. Registry types are stored as static fields in the ''<yarn class_7923>'' or ''<yarn class_2378>'' class, and the identifier is what labels your content. Content is an instance of whatever you're adding. Specifically for item, the syntax is ''<yarn class_2378>#<yarn method_10230>(<yarn class_7923>.<yarn field_41178>, <yarn class_2960>, <yarn class_1792>)''. This can be called anywhere as long as it occurs during initialization. The method itself also returns the registered content itself.

For versions since 1.21, an ''Identifier'' is created through ''%%Identifier.of("namespace", "path")%%''. For versions below 1.21, it is created through ''%%new Identifier("namespace", "path")%%'' or ''%%new Identifier("namespace:path")%%''. It will fail if the namespace or path contains illegal characters.

<yarncode java [enable_line_numbers="true"]>
public class ExampleMod implements ModInitializer {

    // an instance of our new item
    public static final class_1792 CUSTOM_ITEM = new class_1792(new class_1792.class_1793());

    @Override
    public void onInitialize() {
        // For versions below 1.21, please replace ''Identifier.of'' with ''new Identifier''
        class_2378.method_10230(class_7923.field_41178, Identifier.of("tutorial", "custom_item"), CUSTOM_ITEM);
    }
}
</yarncode>
Your new item has now been added to Minecraft. Run the run config ''Minecraft Client'' or ''runClient'' Gradle task to see it in action, execute the command ''/give @s tutorial:custom_item'' in game.

For more simplicity, you can simplify your code by directly registering them when assigning the fields, as ''Register.register'' will also return the registered object:
<yarncode java [enable_line_numbers="true"]>
public class ExampleMod implements ModInitializer {

    // an instance of our new item
    public static final class_1792 CUSTOM_ITEM =
      // For versions below 1.21, use ''new Identifier("tutorial", "custom_item")''.
      class_2378.method_10230(class_7923.field_41178, Identifier.of("tutorial", "custom_item"),
        new class_1792(new class_1792.class_1793()));

    @Override
    public void onInitialize() {
    }
}
</yarncode>

===== Best practice of registering items =====
In the code above, you simply created //one// item. However, it is not convenient if you have //many// items in your mod, as you need to register and create an ''Identifier'' instance each time. Therefore, we can create a specific class to store item objects, such as ''ModItems'' or ''TutorialItems'', and write a simple ''register'' method to conveniently register items. This is quite common in actual mod development. You may also check vanilla ''Items'' class to see how Minecraft completes it in a similar way.

In this example, create a ''TutorialItems'' class and refer to the class in the ''ModInitializer''.

<yarncode java [enable_line_numbers="true"]>
public final class TutorialItems {

    private TutorialItems() {}
    
    // an instance of our new item
    public static final class_1792 CUSTOM_ITEM = register("custom_item", new class_1792(new class_1792.class_1793()));

    public static <T extends Item> T register(String path, T item) {
        // For versions below 1.21, please replace ''Identifier.of'' with ''new Identifier''
        return class_2378.method_10230(class_7923.field_41178, Identifier.of("tutorial", path), item);
    }
    
    public static void initialize() {
    }
}
</yarncode>

Remember to refer to some methods or fields in the mods initializer so as to statically load the class ''TutorialItems''.
<yarncode java [enable_line_numbers="true"]>
public class ExampleMod implements ModInitializer {
    @Override
    public void onInitialize() {
        TutorialItems.initialize();
    }
}
</yarncode>

> **Note:** Some experienced users may decide to use reflection to automatically register all static fields of a class. This is also a preferable way, but should be used with caution.

===== Creating Items in 1.21.2+ =====

Since 1.21.2, the item registration is tutally rewrited. You have to store a ''RegistryKey'' in your ''Item.Settings'', so the models and translation keys will be correctly stored in item components. Otherwise, you may see the following exceptions and Minecraft does not run:

<code>
java.lang.NullPointerException: Item id not set
</code>

To make it run correctly, you should write like below:

<code java>
public final class TutorialItems {
  private TutorialItems() {
  }

  public static final Item CUSTOM_ITEM = register("custom_item", Item::new, new Item.Settings());

  public static Item register(String path, Function<Item.Settings, Item> factory, Item.Settings settings) {
    final RegistryKey<Item> registryKey = RegistryKey.of(RegistryKeys.ITEM, Identifier.of("tutorial", path));
    return Items.register(registryKey, factory, settings);
  }

  public static void initialize() {
  }
}
</code>

In the method ''Items.register'', the registry key will be written in the ''settings'' first, and then use that ''settings'' to create the item.

===== Adding model and textures =====

If you registered your item properly in the first step, you can successfully get your item by typing command ''/give @s tutorial:custom_item''. You will find it has missing texture, and Minecraft will complain about a missing texture file in a fashion similar to this:

    [Server-Worker-1/WARN]: Unable to load model: 'tutorial:custom_item#inventory' referenced from: tutorial:custom_item#inventory: java.io.FileNotFoundException: tutorial:models/item/custom_item.json

That's because we haven't provided the item with textures and models. Therefore, you need to define the item model json and provide a texture image. You're going to need to add these to your resource directory. The direct path of each is:

  * Item model: ''.../resources/assets/tutorial/models/item/custom_item.json''
  * Item texture: ''.../resources/assets/tutorial/textures/item/custom_item.png''

Our example texture can be found [[https://i.imgur.com/CqLSMEQ.png|here]].

A basic item model template is:
<code JavaScript>
{
  "parent": "item/generated",
  "textures": {
    "layer0": "tutorial:item/custom_item"
  }
}
</code>
The ''parent'' of your item model changes how it's rendered in the hand and comes in useful for things like block items in the inventory. ''item/generated'' is used for many simple items. ''item/handheld'' is used for tools that are held from the bottom left of the texture. In the json, ''textures/layer0'' is the location of your image file.

===== Creating an Item class =====

You have created a simple item, and learned how to change some basic properties. But maybe you want it to have more behaviors. Therefore, you will need to create an item class. The default constructor requires an ''Item.Settings'' object.
<yarncode java [enable_line_numbers="true"]>
public class CustomItem extends class_1792 {
    public CustomItem(class_1793 settings) {
        super(settings);
    }
}
</yarncode>

A practical use-case for a custom item class would be making the item play a sound when you use it:
<yarncode java [enable_line_numbers="true"]>
public class CustomItem extends class_1792 {
    public CustomItem(class_1793 settings) {
        super(settings);
    }

    // write this if the version is below 1.21.2:
    @Override
    public class_1271<class_1799> method_7836(class_1937 world, class_1657 user, class_1268 hand) {
        user.method_5783(class_3417.field_14983, 1.0F, 1.0F);
        return class_1271.method_22427(user.method_5998(hand));
    }
    
    // write this if the version is 1.21.2 or higher:
    @Override
    public ActionResult use(World world, PlayerEntity user, Hand hand) {
        user.playSound(SoundEvents.BLOCK_WOOL_BREAK, 1.0F, 1.0F);
        return ActionResult.SUCCESS;
    }
}
</yarncode>

Replace the old <yarn class_1792> object with an instance of your new item class:
<yarncode java [enable_line_numbers="true"]>
public final class TutorialItems {
    [...]

    // an instance of our new item
    
    // For versions below 1.21.2:
    public static final CustomItem CUSTOM_ITEM = register("custom_item", new CustomItem(new class_1792.class_1793()));
    
    // For versions since 1.21.2:
    public static final CustomItem CUSTOM_ITEM = register("custom_item", CustomItem::new, new class_1792.class_1793());
    [...]
}
</yarncode>
If you did everything correctly, using the item should now play a sound. You can also [[tooltip|add some tooltips]] for the item based on your item class.

===== Item components =====
Sometimes you may need to add some default components for the item, such as max stack size or fire durability. This can be done by calling ''component'' method in ''Item.Settings''. Detailed information about item components can be found in [[https://docs.fabricmc.net/develop/items/custom-data-components|the tutorial in Fabric docs]].

In this example, the item will be unbreakable by default, while hiding tooltips about it.
<yarncode java>
    // For versions below 1.21.2:
    public static final CustomItem CUSTOM_ITEM = register("custom_item", new CustomItem(new class_1792.class_1793()
        .component(DataComponentTypes.UNBREAKABLE, new UnbreakableComponent(true))));
    // For versions since 1.21.2:
    public static final Item CUSTOM_ITEM = register("custom_item", CustomItem::new, new Item.Settings()
        .component(DataComponentTypes.UNBREAKABLE, new UnbreakableComponent(true)));
</yarncode>

Specifically, max stack size can be simply set by calling ''maxCount'' method (which is valid also before 1.20.5). Note that if your item is damageable you cannot specify a maximum stack size or the game will throw a ''RuntimeException''.

<yarncode java [enable_line_numbers="true"]>
public class ExampleMod implements ModInitializer {
    // An instance of our new item, where the maximum stack size is 16
    
    // For versions below 1.21.2:
    public static final CustomItem CUSTOM_ITEM = register("custom_item", new CustomItem(new class_1792.class_1793().maxCount(16)));
    // For versions since 1.21.2:
    public static final Item CUSTOM_ITEM = register("custom_item", CustomItem::new, new Item.Settings().maxCount(16));
    [...]
}
</yarncode>

===== Make your item become fuel, or compostable =====

If you want to make it a fuel so that it can be used in a furnace, you can register in ''FuelRegistry'' when initializing the mod, for example:
<code java>
public class ExampleMod implements ModInitializer {
    [...]
    
    // For versions below 1.21.2
    @Override
    public void onInitialize() {
        [...]
        FuelRegistry.INSTANCE.add(TutorialItems.CUSTOM_ITEM, 300);
    }
}
</code>

However, in practice, when you have many items to register, as registering quantities of items may be effort-consuming and messy, you can consider placing the codes in a separate method, instead of writing like above.

In versions below 1.21.2, you need to use Fabric API's ''FuelRegistry.INSTANCE''.
<code java>
public final class TutorialItems {
    [...]
    
    // For versions below 1.21.2
    public static void registerFuels() {
        FuelRegistry.INSTANCE.add(CUSTOM_ITEM, 300);
    }
}
</code>

In versions since 1.21.2, use Fabric API's ''FuelRegistryEvents'':
<code java>
public final class TutorialItems {
    [...]
    
    // For versions since 1.21.2
    public static void registerFuels() {
        FuelRegistryEvents.BUILD.register((builder, context) -> {
            // You can add multiple items at once in this lambda.
            builder.add(CUSTOM_ITEM, 300);
        });
    }
}
</code>

And then refer to this method in your ''ModInitializer'':
<code java>
public class ExampleMod implements ModInitializer {
    [...]
    
    @Override
    public void onInitialize() {
        [...]
        TutorialItems.registerFuels();
    }
}
</code>

Similarly, you can use a ''CompostingChanceRegistry'' to make it compostable in a composter.
===== Next Steps =====
[[tutorial:itemgroup|Add your item to your own ItemGroup]].