tutorial:interface_injection
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| tutorial:interface_injection [2025/02/12 18:42] – Add node on unicode escape for $ earthcomputer | tutorial:interface_injection [2025/11/10 03:38] (current) – Add info on how to inject generic interfaces earthcomputer | ||
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| ======= Interface Injection ======= | ======= Interface Injection ======= | ||
| - | This is a new technique | + | ===== Overview ===== |
| - | More specifically, | + | |
| + | Interface injection | ||
| + | More specifically, | ||
| As result the target class will acquire all the methods of the interface, as if it always had them. | As result the target class will acquire all the methods of the interface, as if it always had them. | ||
| Interface injection is a compile time only feature, this means that a Mixin should also be used to implement the interface into the target class. | Interface injection is a compile time only feature, this means that a Mixin should also be used to implement the interface into the target class. | ||
| Line 8: | Line 10: | ||
| This is particularly useful for libraries, with this you can add new methods to existing classes and use them without the need of casting or reimplementing the interface every time. | This is particularly useful for libraries, with this you can add new methods to existing classes and use them without the need of casting or reimplementing the interface every time. | ||
| - | Let's explain better with an example: | + | Fabric API takes advantage of this technique. For example, '' |
| + | ===== Example Goal ===== | ||
| The scope of this example is to add the following method into ''< | The scope of this example is to add the following method into ''< | ||
| This, normally, is not possible because ''< | This, normally, is not possible because ''< | ||
| < | < | ||
| - | Optional< | + | Optional< |
| </ | </ | ||
| + | |||
| + | ===== Step 1: Create the Interface ===== | ||
| To add the method into the class, first of all you need to create an interface with it: | To add the method into the class, first of all you need to create an interface with it: | ||
| Line 23: | Line 28: | ||
| public interface BucketEmptySoundGetter { | public interface BucketEmptySoundGetter { | ||
| - | // The methods in an injected interface MUST be default, | + | default Optional< |
| - | // otherwise code referencing them won't compile! | + | |
| - | default Optional< | + | |
| return Optional.empty(); | return Optional.empty(); | ||
| } | } | ||
| } | } | ||
| </ | </ | ||
| + | |||
| + | :!: The method body in the interface may not be used because it will be overridden by the mixin class. However, you must specify the method body, which means the method must be '' | ||
| + | |||
| + | ℹ️ It's highly recommended to add a dollar-character or underscore character with the mod name as the prefix or suffix of the method name, in order to avoid method name conflict with other mods. | ||
| + | |||
| + | ===== Step 2: Implement the Interface with a Mixin ===== | ||
| Now you need to implement this interface into ''< | Now you need to implement this interface into ''< | ||
| Line 35: | Line 44: | ||
| < | < | ||
| @Mixin(class_3609.class) | @Mixin(class_3609.class) | ||
| - | public | + | abstract |
| @Override | @Override | ||
| - | public Optional< | + | public Optional< |
| //This is how to get the default sound, copied from BucketItem class. | //This is how to get the default sound, copied from BucketItem class. | ||
| return Optional.of(((class_3609) (Object) this).method_15791(class_3486.field_15518) ? class_3417.field_15010 : class_3417.field_14834); | return Optional.of(((class_3609) (Object) this).method_15791(class_3486.field_15518) ? class_3417.field_15010 : class_3417.field_14834); | ||
| Line 43: | Line 52: | ||
| } | } | ||
| </ | </ | ||
| + | |||
| + | ===== Step 3: Inject the Interface in '' | ||
| Lastly you need to inject the interface into ''< | Lastly you need to inject the interface into ''< | ||
| - | The following snippet can be added to your fabric.mod.json file to add one or more interfaces to the ''< | + | The following snippet can be added to your '' |
| Note that all class names here must use the " | Note that all class names here must use the " | ||
| - | <code json [enable_line_numbers=" | + | < |
| { | { | ||
| " | " | ||
| Line 57: | Line 68: | ||
| } | } | ||
| </ | </ | ||
| + | |||
| + | :!: Sometimes, your interface injections may need to include the '' | ||
| + | |||
| + | ==== Generic interfaces ==== | ||
| + | |||
| + | If your interface has generics, you can specify them when you add the injected interface. For this, you need to add ''<>'' | ||
| + | |||
| + | ^ Description | ||
| + | | Class type | '' | ||
| + | | Array type | '' | ||
| + | | Primitive type (may appear as array elements) | '' | ||
| + | | Type variable | ||
| + | | Generic class type | '' | ||
| + | | Wildcard | ||
| + | | Extends wildcard bound | ''? | ||
| + | | Super wildcard bound | ''? | ||
| + | |||
| + | Here is a full example using generics: | ||
| + | <code json fabric.mod.json [enable_line_numbers=" | ||
| + | { | ||
| + | " | ||
| + | " | ||
| + | " | ||
| + | } | ||
| + | } | ||
| + | } | ||
| + | </ | ||
| + | which would generate the implementation: | ||
| + | < | ||
| + | public class class_3609 implements MyGenericInterface<? | ||
| + | // ... | ||
| + | } | ||
| + | </ | ||
| + | |||
| + | ===== Step 4: Using the Injected Method ===== | ||
| Now you can use the new method: | Now you can use the new method: | ||
| < | < | ||
| - | Optional< | + | Optional< |
| </ | </ | ||
| - | You could also override this method in classes extending <yarn class_3609> | ||
| - | Sometimes, your interface injections may need to include the '' | + | You could also override |
| + | |||
tutorial/interface_injection.1739385772.txt.gz · Last modified: 2025/02/12 18:42 by earthcomputer