Safe_handle.lua

function getWrappedFunction(f)
    -- this function will be called with handle, but we want to call it with raw reference
    return function(handle, ...) return f(handle.cppRef, ...) end
end

local memoizedEntityCppFuncs = {}

function createHandle(e)
    local handle = {
        cppRef = e,
        isValid = true
    }

    local mt = {}
    mt.__index = function(handle, key)
        if not handle.isValid then
            error("Handle is invalid!", 2)
        end

        -- memoizing functions speeds this up a lot
        local memF = memoizedEntityCppFuncs[key]
        if not memF then
            memF = getWrappedFunction(Entity[key])
            memoizedEntityCppFuncs[key] = memF
        end
        return memF
    end

    setmetatable(handle, mt)
    return handle
end

function onEntityDeleted(handle)
    handle.isValid = false
end

function test(handle)
    print("Calling through handle:", handle:getName())
end

function test2(e)
    print("Calling through raw reference:", e:getName())
end