Working with Source Code (UE C++)

Warning

The source code for Unreal Engine requires a plugin to be installed to function. If you get compilation errors, make sure the plugin is installed and enabled.

Accessing game data during runtime is possible by utilizing the generated source code.

This section provides examples using default class names, but it is possible to customize class names during the source code generation process. Additionally, this customization allows to avoid naming collisions with existing code.

Loading Game Data

The following C++ code creates UGameData class and loads your game data into memory.

IFileManager& FileManager = IFileManager::Get();

const FString GameDataFilePath = TEXT("./RpgGameData.gdjs");  // or .json
const TUniquePtr<FArchive> GameDataStream = TUniquePtr<FArchive>(FileManager.CreateFileReader(*GameDataFilePath, EFileRead::FILEREAD_None));

UGameData* GameData = NewObject<UGameData>();

FGameDataLoadOptions Options;
Options.Format = EGameDataFormat::Json;
// Options.Patches.Add(PatchStream1);
// Options.Patches.Add(PatchStream2);
// ...

if (!GameData->TryLoad(GameDataStream.Get(), Options))
{
  // Handle failure
}

The file RpgGameData.gdjs could be published game data or original database file (.gdjs or .gdmp).

Accessing Documents

You can access your documents as a list:

auto AllHeroes = GameData->AllHeroes // -> TMap<string, UHero>
auto Heroes = GameData->Heroes // -> TMap<string, UHero>

Settings schemas are accessed by name:

auto StartingHeroes = GameData->StartingSet.Heroes; // -> TMap<string, UHero>

Formulas

Formulas are currently not supported.

Extension of Generated Code

Customizing Metadata

You can append additional or replace existing macro to the generated classes and their properties by modifying the Specification field of the related schema or property.

Metadata annotations are specified using the uecppAttribute key in the Specification string, which uses the application/x-www-form-urlencoded format.

To help construct the correct value, you can use a spreadsheet formula (e.g., in Excel or Google Sheets):

# Place your attribute in cell A1
=TEXTJOIN("&", 1, IF(ISBLANK(A1), "", "&uecppAttribute=" & ENCODEURL(A1)))

Alternatively, use JavaScript to generate the encoded string:

const params = new URLSearchParams();
params.append("uecppAttribute", "UPROPERTY(EditAnywhere, Meta = (Bitmask))");
console.log(params.toString());
// → uecppAttribute=UPROPERTY%28EditAnywhere%2C+Meta+%3D+%28Bitmask%29%29

After obtaining the encoded string, append it to the existing Specification value.

Example:

# Original Specification value:
icon=material&group=Metadata

# New attribute to add:
uecppAttribute=UCLASS%28BlueprintType%29

# Final Specification value:
icon=material&group=Metadata&uecppAttribute=UCLASS%28BlueprintType%29

These metadata annotations will be emitted directly into the generated C++ code, attached to the appropriate class or property.