Home

ScriptEvent_Transpiler

A tool that simplifies the creation of ScriptEvent lua files for O3DE Game Projects.

Motivation

In O3DE you can use Script Events to create EBuses in Lua. With those EBuses you can send/receive events across lua & ScriptCanvas scripts. Script Events replace the old Gameplay Notification Bus.

THE PROBLEM: It is tedious to declare Script Events in a LUA file. You have to declare each function, parameter, and return type line by line.
THE SOLUTION: It would be nice if We could write a simple lua file that declares an interface that We'd like to be the API for any given Script Event. And with the magic of a transpiler We could generate the boiler plate ScriptEvent definition file.

SIMILAR SITUATIONS:

For the sake of analogy, here is a list of similar scenarios where people use a transpiler/compiler that takes an input "interface" file and generates a more complicated class file.

• Interface file: *.proto ---> Google Protocol Buffer Compiler --> A class file in JAVA, or CPP, or Python, etc
• Interface file: *.aidl ---> AIDL Compiler --> A class file in JAVA, CPP, etc.
• Interface file: *.idl ---> Microsoft MIDL Compiler ---> A COM interface file.

I hope you get the idea by now...

Which version of ScriptEvent_Transpiler? (C++ or Python)

TL;DR: Try the Precompiled Binary (Win64) which was generated from the C++ version.

The file (CppApp/README.md) contains instructions on how to compile the C++ version from scratch.

If using Linux, then try using the Python version. The Python version can also be used on Windows. If using python replace "ScriptEvent_Transpiler_Release.exe" with "python main.py"

Now, let's transpile the sample interface file located in Samples/demo_interface.lua, the idea is to generate a ScriptEvent lua file.

USAGE 1

ScriptEvent_Transpiler> ScriptEvent_Transpiler_Release.exe -e MyBroadcastBus -Samples\demo_interface.lua Samples

One file is generated inside the .Samples/ directory:

• MyBroadcastBus.lua <-- This is the non-addressable Broadcast type of ScriptEvent lua file. Callers would do MyBroadcastBus.Broadcast.Function(...)

USAGE 2

ScriptEvent_Transpiler> ScriptEvent_Transpiler_Release.exe -e MyBroadcastBus -t Samples\demo_interface.lua Samples

Two Files are generated inside the .Samples/ directory:

• MyBroadcastBus.lua <-- This is the non-addressable Broadcast type of ScriptEvent lua file. Callers would do MyBroadcastBus.Broadcast.Function(...)
• MyBroadcastBus_subclass.lua <-- An example class file on how to listen or respond to events sent to the MyBroadcastBus Bus. You should place MyBroadcastBus.lua nested somewhere in your GAME_PROJECT/Scripts/... folder.

USAGE 2

ScriptEvent_Transpiler> ScriptEvent_Transpiler_Release.exe -e MyEventBus -a EntityId -t Samples\demo_interface.lua Samples

Two Files are generated inside .Samples\

• MyEventBus.lua <-- This is the EntityId addressable Event type of ScriptEvent lua file. Callers would do MyEventBus.Event.Function(SomeEntityId, ...)
• MyEventBus_subclass.lua <-- An example class file on how to listen or respond to events sent to the MyEventBus Bus. You should place MyEventBus.lua nested somewhere in your GAME_PROJECT/Scripts/... folder.