[FVMReflection](API\Plugins\NetcodeUnitTest\FVMReflection) - Reflection Helper



*FObjectProperty * WorldInvProp


FVMReflection - Reflection Helper

Description: The purpose of the reflection helper, is to allow complete access to the UE4 UScript/Blueprint Virtual Machine through reflection, i.e. without directly/statically referencing any classes/structs/variables/etc., referencing them all only by name/string instead, so anything using the VM can be accessed without a dependency on other packages (and without compile fails when something changes).

This is useful/important for writing unit tests that can break or go out of date, without breaking an entire suite of unit tests, and for maintaining permanent backwards compatibility through multiple engine/game codebase updates, and for general debugging.

Operator roles: (... is shorthand for an FVMReflection instance)

  • FVMReflection(Object): Initialize a reflection helper, pointing to the specified object, for use with operators

  • FVMReflection(FStructOnScope): Initialize a reflection helper, pointing to the struct within the specified FStructOnScope

  • FVMReflection(VMReflection): Initialize a reflection helper, by copying another reflection helpers current state

  • ...->*"Property": Point the reflection helper, to the specified property

  • (...->*"Array")["Type"][Element]: Array property element (also specifies the inner array type, for verification)

  • (Type)(...): Cast data the reflection helper points to, to specified type (only way to access data)

  • (Struct*)(void*)(...)["Struct"]: Special cast (void*), for accessing structs (also specify struct type [], for verification)

  • (..., &bError): Outputs to bError, whether any error was encountered this far into parsing

  • (..., &ErrorString): As above, excepts outputs a string containing the entire reflection history and error text

Not yet implemented:

  • (...->*"Function")("Parm1", etc.): Execute the specified function, with the specified parameters. Might not get implemented.

Example: FGuid* ItemGuid = (FGuid*)(void*)(((FVMReflection)->*"WorldInventory"->*"Inventory"->*"Items") ["FFortItemEntry"][0]->"ItemGuid")["FGuid"]);

Setting function parameters: The FFuncReflection class allows you to easily set the parameters for functions, using reflection; this is useful for RPC's, as well as for general local functions called using ProcessEvent etc..

For example: FFuncReflection FuncRefl(PlayerStateObj, TEXT("UndoRemoveCardFromHandAtIndex"));

FVMReflection->*"CardData"->*"CardGuid"->*"A" = 1;

PlayerStateObj->ProcessEvent(FuncRefl.GetFunc(), FuncRefl.GetParms()); Example of how the reflection helper makes code more succinct:

New code (reflection helper): // Reflection for AFortPlayerController->QuickBars AActor* QuickBars = (AActor*)(UObject*)(FVMReflection)->*"QuickBars");

// Reflection for AFortPlayerController->WorldInventory->Inventory->Items->ItemGuid FGuid* EntryItemGuidRef = (FGuid*)(void*)(((FVMReflection) ->*"WorldInventory"->*"Inventory"->*"Items")["FFortItemEntry"][0]->*"ItemGuid")["FGuid"]);

Old code (manual reflection): // Reflection for AFortPlayerController->QuickBars FObjectProperty* QuickBarsProp = FindFProperty(UnitPC->GetClass(), TEXT("QuickBars")); UObject** QuickBarsRef = (QuickBarsProp != NULL ? QuickBarsProp->ContainerPtrToValuePtr(UnitPC.Get()) : NULL); AActor* QuickBars = (QuickBarsRef != NULL ? Cast(*QuickBarsRef) : NULL);

// Reflection for AFortPlayerController->WorldInventory->Inventory->Items->ItemGuid /**

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