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9105 :: Map complex C++ types into Nim

• jmgomez (orginal) [2022-04-14T19:15:30+02:00] view original

  How do you map in Nim a function with this signature:

  
  
  void FunctionName(UObject* Context, FFrame& Stack, void*const Result) {..}
  
  
  Run

  And then cast the type so it can be accepted as one argument only of FNativeFuncPtr which comes defined as:

  
  
  typedef void (*FNativeFuncPtr)(UObject* Context, FFrame& TheStack, RESULT_DECL);
  
  
  Run

  So I can create a Function in nim like so

  
  
  proc SetNativeFunc*(ufunc: UFunction, funcPtr: FNativeFuncPtr) : void {.importcpp: "#->SetNativeFunc(#)", header:  "UObject/Class.h" .}
  
  
  proc NimFunctionToReplace*(context:ptr UObject, stack:ptr FFrame, result:ptr void)  = ....
  
  
  SetNativeFunc(NimFunctionToReplace)
  
  Run

  Thanks,

  Juan

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• jmgomez (orginal) [2022-04-14T23:43:23+02:00] view original

  Got it working until here

  
  
  cannot convert argument 1 from 'void (__cdecl *)(UObject *,FFrame *,void *)' to 'void (__cdecl *)(UObject *,FFrame &,void *)'
  
  
  Run

  I imported it like that:

  
  
  type FFrame* {.importcpp: "FFrame", inheritable, pure, byref, header:  "UObject/Stack.h".} = object
      Code : ptr uint8
  
  Run

  
  
  proc MakeFNativeFuncPtr*(fun:proc (context:ptr UObject, stack: FFrame,  result: pointer):void {. cdecl .}) : FNativeFuncPtr {.importcpp: "UReflectionHelpers::MakeFNativeFuncPtr(@)", header:  "NimObjectBindTest.h" .}
  
  Run

  This is the Cpp definition:

  
      
      static FNativeFuncPtr MakeFNativeFuncPtr(void (FnPtr)(UObject* Context, FFrame& TheStack, void* Result));
  
  Run

  If I change the ref in Cpp I can do a reinterpret_cast but I got a crash and not sure if it's because of it or something else. Is there a way to tell nim to export an argument as a C++ ref (&)? Any direction will be appreciated. Thanks, Juan

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• veksha (orginal) [2022-04-15T04:32:56+02:00] view original

  what if you try to write stack: var FFrame instead of stack: FFrame ?

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• sls1005 (orginal) [2022-04-15T04:50:52+02:00] view original

  var FFrame is mapped to FFrame& in C++ (but it's a pointer with the C backend)

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• jmgomez (orginal) [2022-04-15T11:32:25+02:00] view original

  Yes, that did work!! Thanks! Is that on the docs? Couldnt find it

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• sls1005 (orginal) [2022-04-15T11:49:40+02:00] view original

  I learned it by reading the generated C code.

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