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tutorial:mixin_injects

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tutorial:mixin_injects [2020/08/26 04:55] – Add a note on constructor descriptor siglongtutorial:mixin_injects [2025/09/24 12:13] (current) – Mark page as WIP in preparation for major review and edits upcoming gauntrecluse
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-====== Mixin Injects ======+FIXME //This page is under heavy rewrites due to prior edits being from 2022, and it thus contains seriously outdated advice. This page may change very suddenly and should only be taken with a grain of salt.// 
 + 
 +====== Mixin Injects (WIP) ======
  
 ===== Introduction ===== ===== Introduction =====
-Injects allows you to place custom code at a specified position inside an existing method. For a working example, view the [[https://fabricmc.net/wiki/tutorial:mixin_injects#practical_example|Practical Example]] category at the bottom of this page. The standard form of an inject is as shown:+Injects allows you to place custom code at a specified position inside an existing method. For a working example, view the [[tutorial:mixin_injects#practical_example|Practical Example]] category at the bottom of this page. The standard form of an inject is as shown:
  
 <code java> <code java>
-@Inject(method = "", at = @At("INJECTION POINT REFERENCE"))+@Inject(method = "METHOD NAME OR SIGNATURE", at = @At("INJECTION POINT REFERENCE"))
 private void injectMethod(METHOD ARGS, CallbackInfo info) { private void injectMethod(METHOD ARGS, CallbackInfo info) {
  
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 | D | double | double-precision floating-point value | | D | double | double-precision floating-point value |
 | F | float | single-precision floating-point value | | F | float | single-precision floating-point value |
-| I | int | integer | +| I | int | signed integer | 
-| J | long | long integer |+| J | long | signed long integer |
 | L//ClassName//; | reference | an instance of //ClassName// | | L//ClassName//; | reference | an instance of //ClassName// |
 | S | short | signed short | | S | short | signed short |
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 | [ | reference | one array dimension | | [ | reference | one array dimension |
  
-A method descriptor is comprised of the method name, followed by a set of parentheses containing the input types, followed by the output type. A method defined in Java as ''Object m(int i, double[] d, Thread t)'' would have the method descriptor ''m(I[DLjava/lang/Thread;)Ljava/lang/Object;''.+A method descriptor is comprised of the method name, followed by a set of parentheses containing the parameter types, followed by the return type. A method defined in Java as ''Object m(int i, double[] d, Thread t)'' would have the method descriptor ''m(I[DLjava/lang/Thread;)Ljava/lang/Object;''.
  
-//@Inject// methods always have a void return type. The method name does not matter; using something that describes what the inject does is best. The target method's arguments are placed first in the method's header, followed by a ''CallbackInfo'' object. If the target method has a return type (T), ''CallbackInfoReturnable<T>'' is used instead of ''CallbackInfo''.+In the case that the return type is void, you need to use V (Void Descriptor Type) as the type (for example, ''void foo(String bar)'' would become ''foo(Ljava/lang/String;)V''). 
 + 
 +Generics' types are left out, as generics don't exist on runtime. So ''Pair<Integer, ? extends Task<? super VillagerEntity>‍>'' would become ''Lcom/mojang/datafixers/util/Pair''. 
 + 
 +''@Inject'' methods always have a void return type. The method name does not matter and neither does the access modifier; using something that describes what the inject does is best. The target method's arguments are placed first in the method's header, followed by a ''CallbackInfo'' object. If the target method has a return type (T), ''CallbackInfoReturnable<T>'' is used instead of ''CallbackInfo''.
  
 === Returning & Cancelling from Inject === === Returning & Cancelling from Inject ===
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 === Injecting into Constructors === === Injecting into Constructors ===
-To inject into a constructor, use ''<init>()V'' as the method target, with ''()'' containing the constructor argument descriptors. When injecting into constructors, ''@At'' must be set to either ''TAIL'' or ''RETURN''. Note that some classes have methods named ''init'' which are different from ''<init>''. Don't get confused!+To inject into a constructor, use ''<init>()V'' as the method target, with ''()'' containing the constructor argument descriptors. When injecting into constructors, ''@At'' must be set to either ''TAIL'' or ''RETURN''. No other forms of injection are officially supported. Note that some classes have methods named ''init'' which are different from ''<init>''. Don't get confused! 
 + 
 +To inject into a static constructor, use ''<clinit>'' as the method name.
  
 ===== Practical Example ===== ===== Practical Example =====
tutorial/mixin_injects.1598417747.txt.gz · Last modified: 2020/08/26 04:55 by siglong