iOS Save Game Getting Deleted or Corrupted Somehow

Development Platform & Builds Mobile
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1

I’ve released a beta version of my game and users are complaining about save games being deleted. This is really confusing because I have never been able to reproduce the issue locally, save games for me always worked. I am not doing anything special. I init, load, and write my save game with the following code:

void ULlamagotchiGameInstance::InitSaveGame_Implementation()
{
	if (SaveInstance == nullptr)
	{
		if (!LoadSaveGame())
		{
			SaveInstance = CreateSaveGame();
			ensure(SaveInstance != nullptr);
			SaveInstance->bIsFirstLaunchInLevel = true;	   // Game launching for the first time
		}
	}
}

bool ULlamagotchiGameInstance::LoadSaveGame()
{
	SaveInstance = Cast<ULGSaveGame>(UGameplayStatics::LoadGameFromSlot(kGameSlotName, 0));
	return SaveInstance != nullptr;
}
bool ULlamagotchiGameInstance::WriteSaveGameToDisk(APetCharacter* Pet, ALlamagotchiPlayerController* PlayerController, APawn* PlayerPawn)
{
	if (!UpdateSaveInMemory(Pet, PlayerController, PlayerPawn))
	{
		UE_LOG(LogLgGameInstance, Log, TEXT("Savegame write to memory failed"));
		return false;
	}
	
	// Save game
	if(UGameplayStatics::SaveGameToSlot(SaveInstance, kGameSlotName, 0))
	{
		UE_LOG(LogLgGameInstance, Log, TEXT("Savegame successfully saved to disk"));
		return true;
	}

	UE_LOG(LogLgGameInstance, Error, TEXT("Savegame write to disk failed"));
	return false;
}

bool ULlamagotchiGameInstance::UpdateSaveInMemory(APetCharacter* Pet, ALlamagotchiPlayerController* PlayerController,
	APawn* PlayerPawn)
{
	UE_LOG(LogLgGameInstance, Log, TEXT("Updating save game in memory"));

	if (!SaveInstance)
	{
		UE_LOG(LogLgGameInstance, Error, TEXT("SaveInstance was null when trying to update save in memory"));
		return false;
	}

	[snip]

	TArray<AActor*> SaveableActors;
	UGameplayStatics::GetAllActorsWithInterface(GetWorld(), USaveableInterface::StaticClass(), SaveableActors);
	for (auto SaveableActor : SaveableActors)
	{
		SaveInstance->ActorSaver(SaveableActor, SaveInstance->CurrentLevel);
	}

	[snip]

	UE_LOG(LogLgGameInstance, Log, TEXT("Updated save game in memory"));

	return true;
}

The only thing I can think of that is a little bit non-standard is I am using a FObjectAndNameAsStringProxyArchive to write my actor data:

/**
 * Save Game Archiver.
 */
struct FLGSaveGameArchive : public FObjectAndNameAsStringProxyArchive
{
	FLGSaveGameArchive(FArchive& InInnerArchive) 
			: FObjectAndNameAsStringProxyArchive(InInnerArchive,true)
	{
		ArIsSaveGame = true;
	}
};

void ULGSaveGame::ActorSaver(AActor* SaveActor, ELgLevel Level)
{
	// All actors passed here need to implement this interface
	ISaveableInterface* ImplementsInterface = Cast<ISaveableInterface>(SaveActor);
	check(ImplementsInterface != nullptr);

	FString UniqueId = FObjectRecord::GenerateUniqueId(SaveActor, Level);
	FObjectRecord& ObjectRecord = UniqueIdToObjectRecords.Emplace(UniqueId);
	ObjectRecord.UniqueId = UniqueId;
	ObjectRecord.Name = SaveActor->GetFName();
	ObjectRecord.Transform = SaveActor->GetTransform();
	ObjectRecord.Class = SaveActor->GetClass();
	ObjectRecord.bShouldSpawn = ISaveableInterface::Execute_GetShouldSpawn(SaveActor);
	ObjectRecord.LevelToSpawnIn = ISaveableInterface::Execute_GetLevelToSpawnIn(SaveActor);
	
	SaveData(SaveActor, ObjectRecord.Data);

    UE_LOG(LogSaveGame, Display, TEXT("Complete Save Actor %s"), *SaveActor->GetName())
}

void ULGSaveGame::SaveData(UObject* Object, TArray<uint8_t>& Data)
{
    if (Object == nullptr) return;

    FMemoryWriter MemoryWriter = FMemoryWriter(Data, true);
    FLGSaveGameArchive MyArchive(MemoryWriter);

    Object->Serialize(MyArchive);
}

If anybody has any suggestions or can offer any tips it would be greatly appreciated. Really scratching my head on this one since I haven’t been able to reproduce locally.

2

Several times I encountered the problem of saving when updating the application.

3

What happened in your case exactly? the save files are written to the documents or library folder both of which are not deleted during app update.

4

Just an update incase anybody encounters a similar problem.

I was able to work around this issue by writing my save game multiple times and then loading the most recent one. This way even if a save game write fails it will just load the last successful save.

Eventually I would like to re-write all of the engine code that uses the low level c file-writing APIs with higher level NSData or NSFileDescriptor based APIs which I think would also solve whatever corner case bug I was running into that was causing writes to fail.

5

ios is tricky because the os can purge files and the save path differs from pc, so a flow that works locally can still lose saves on device. make sure you only Create when no save exists (otherwise you overwrite on every boot), flush after write, and keep a version field so an interrupted write doesnt brick the next launch. advanced save system from fab Save System / Cloud Save / Encryption / Slot management | Fab adds transaction-safe ops with error handling plus slot metadata, so a bad write on mobile returns an error you can recover from instead of silently wiping progress