Bluelua for UE4

Replace the blueprint with Lua, keep it in a consistent way with the blueprint, and switch seamlessly. Accessing UObject's properties and methods with reflection and without the need to generate glue code, more simple and easy to expand.

Android, iOS, Mac, Windows, Linux are supported now.

Used Open Source Libraries

• lua : Lua is a powerful, efficient, lightweight, embeddable scripting language
• luasocket : Network support for the Lua language
• Tencent LuaPanda : Pandora Lua Debugger for VS Code

Features

• Call UFunction directly in lua
• Access UProperty member of UClass/UStruct
• Override BlueprintNativeEvent/BlueprintImplementable in lua
• Override blueprint's function/event in lua
• Override native net replicated event(Server/Client/NetMulticast) in lua
• Override blueprint's net replicated event in lua

How to use

Clone Bluelua to your project's Plugins folder, regenerate project solution and build.

How to inherit C++ with lua

• ILuaImplementableInterface

  All C++ classes that can be used with LUA subclasses need to be inherited from this interface and the corresponding methods are called in the corresponding virtual functions, the main types of overrideing are as follows:

  All C++ classes (or blueprint classes) need to override two important BlueprintNativeEvent: ShouldEnableLuaBinding: should use lua subclass on this C++/Blueprint class. OnInitBindingLuaPath: return corresponding lua file path

  It's optional to override OnInitLuaState: return custom FLuaState wrapper, default use of global lua state

  • Class AActor, see LuaImplementableActor.h

    • Call OnInitLuaBinding in BeginPlay
    • Call OnReleaseLuaBinding in EndPlay
    • Call LuaProcessEvent in ProcessEvent

  • Class UUserWidget, see LuaImplementableWidget.h

    • Call OnInitLuaBinding in NativeConstruct
    • Call OnReleaseLuaBinding in NativeDestruct
    • Call LuaProcessEvent in ProcessEvent

    The UUserWidget class also has a special place where the LatentAction owned by the class is not affected by the pause, so you also need to override NativeTick and call LatentActionManager in the virtual function to handle all LatentAction objects. See TickActions in LuaImplementableWidget.h

  • Class UObject, see RPGAnimNotifyState.h in Demo LuaActionRPG

    • Call OnReleaseLuaBinding in BeginDestroy
    • Call LuaProcessEvent in ProcessEvent
    • Because the Uobject class does not have an initialized virtual function that can be overrided, so it can call OnInitLuaBinding the first time the ProcessEvent is called, as shown in the demo

  • Class UGameInstance, see RPGGameInstanceBase.h in Demo LuaActionRPG

    • Call OnInitLuaBinding in Init
    • Call OnReleaseLuaBinding in Shutdown
    • Call LuaProcessEvent in ProcessEvent

• keyword Super

  When you use Lua to subclass c++ classes or blueprints, there is a temporary global object called Super represent the parent UObject that you can access it's properties and methods. It's only avaliable when lua file is loaded(luaL_loadbuffer), so you need to cache it's reference in your lua file like local MyParent = Super and use MyParent in your lua

• CastToLua

  When you have a UObject in lua and want to know if the object has a lua subclass, you can call CastToLua on that object like local LuaObject = OtherObject:CastToLua(), it returns a lua table represent the lua object if OtherObject has a lua subclass. CastToLua works like cast in blueprint:

  

• Modular lua subcalss

  All lua subclass should implement in modular table and methods should declare with : not ., see see GameInstance.lua in Demo LuaActionRPG

  local m = {}
  
  function m:func()
  end
  
  return m
  

• inheritance in lua

  You can use lua metatable to implement inheritance like you do in C++ or blueprint, see PlayerCharacter.lua and Character.lua in Demo LuaActionRPG

• When a UFUNCTION expose to blueprint, it can has a alias, like BeginPlay in blueprint, it actually called ReceiveBeginPlay. so when you override this function in lua you should use ReceiveBeginPlay not BeginPlay.

Samples

• LuaActionRPG: Epic's ActionRPG demo in lua implementation, still work in progress
• BlueluaDemo: benchmark and test

TODO

• expose lua file reader to project, do not assume lua files under ProjectContent folder
• hot reload lua
• optimize OnProcessLuaOverrideEvent when find lua function

中文版使用介绍

使用介绍