Use the online subsystem to log in - Login with single platform auth - (Unreal Engine module)

Last updated on March 24, 2025

Review the subsystem​

In the Login with device ID module, you set up a subsystem called AuthEssentialsSubsystem_Starter for device ID login. Since the single platform auth login has similar functionalities, you can reuse the subsystem to handle it.

There are no action steps in this page, the steps below are to point out the logic of the AuthEssentialsSubsystem_Starter class. Feel free to skip to the next page if you already know the flow.

  1. Inside the AuthEssentialsSubsystem_Starter class, you will find the SetAuthCredentials() function. This function is used to set the credentials for the login process through the parameters LoginMethod, Id, and Token.

    void UAuthEssentialsSubsystem_Starter::SetAuthCredentials(const EAccelByteLoginType& LoginMethod, const FString& Id, const FString& Token) 
    {
        Credentials.Type = (LoginMethod == EAccelByteLoginType::None) ? TEXT("") : FAccelByteUtilities::GetUEnumValueAsString(LoginMethod);
        Credentials.Id = Id;
        Credentials.Token = Token;
    }

  2. After calling the the function above, you can call the Login() function. This function takes the credentials set in the previous function and handles the login process using AccelByte Gaming Services (AGS) Online Subsystem.

    void UAuthEssentialsSubsystem_Starter::Login(const APlayerController* PC, const FAuthOnLoginCompleteDelegate& OnLoginComplete)
    {
        if (!ensure(IdentityInterface.IsValid()))
        {
            FString Message = TEXT("Cannot login. Identity interface is not valid.");
            UE_LOG_AUTH_ESSENTIALS(Warning, TEXT("%s"), *Message);
            OnLoginComplete.ExecuteIfBound(false, *Message);
            return;
        }

        const ULocalPlayer* LocalPlayer = PC->GetLocalPlayer();
        ensure(LocalPlayer != nullptr);
        int32 LocalUserNum = LocalPlayer->GetControllerId();
        
        IdentityInterface->AddOnLoginCompleteDelegate_Handle(LocalUserNum, FOnLoginCompleteDelegate::CreateUObject(this, &UAuthEssentialsSubsystem_Starter::OnLoginComplete, OnLoginComplete));
        IdentityInterface->Login(LocalUserNum, Credentials);

        /*
         * Logout On Game Exit
         * Workaround for the lobby not properly disconnecting when closing the PIE game.
         */
        if (UAccelByteWarsGameInstance* ByteWarsGameInstance = Cast<UAccelByteWarsGameInstance>(GetGameInstance()); ensure(ByteWarsGameInstance))
        {
            ByteWarsGameInstance->OnGameInstanceShutdownDelegate.AddWeakLambda(this, [this, LocalUserNum]()
            {
                IdentityInterface->Logout(LocalUserNum);

                UE_LOG_AUTH_ESSENTIALS(Warning, TEXT("Logging out local player %d"), LocalUserNum);
            });
        }
    }

  3. The OnLoginComplete() function is called when the login process is completed. This function will execute the OnLoginComplete delegate with the login result.

    void UAuthEssentialsSubsystem_Starter::OnLoginComplete(int32 LocalUserNum, bool bLoginWasSuccessful, const FUniqueNetId& UserId, const FString& LoginError, const FAuthOnLoginCompleteDelegate OnLoginComplete)
    {
        if (bLoginWasSuccessful)
        {
            UE_LOG_AUTH_ESSENTIALS(Log, TEXT("Login user successful."));
        }
        else
        {
            UE_LOG_AUTH_ESSENTIALS(Warning, TEXT("Login user failed. Message: %s"), *LoginError);
        }

        IdentityInterface->ClearOnLoginCompleteDelegates(LocalUserNum, this);
        OnLoginComplete.ExecuteIfBound(bLoginWasSuccessful, LoginError);
    }

In the next section, you will utilize the functions above to implement the single platform auth login.

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