cpp-callback-script is a sample C++ application that is extended by a Lua script.

To run the sample, you need to have the following libraries installed:

• Lua
• Sol2

The sample application provides an abstraction to separate functionality into several modules with the help of Environment and EnvironmentClient classes.

Such a separation allows one to provide parts of the application either as a C++ code, or a Lua one.

The application has Environment that provides a member function with the following signature: Strings call(const String &key, const Strings &values).

The function passes a list of string values (std::vector) to the specified key and returns a result as another list of string values.

The application also has EnvironmentClient that serves as a callback container for third parties wishing to interact indirectly through Environment.

EnvironmentClient has the following callbacks:

• callbackRespondsToKey returns a list keys this particular EnvironmentClient instance responds to
• callbackCall returns a list of keys as a result of running provided callback

The callbacks use std::function to remove the need for third parties to inherit EnvironmentClient to specify custom behaviour.

runCPP function inside main.cpp registers two EnvironmentClient instances that respond to different keys.

runSol function inside main.cpp registers Environment, EnvironmentClient with Lua (using Sol2), and then runs script.lua.

script.lua, in its turn, creates an instance of EnvironmentClient that responds to a new key.