[Lua + GObject] Canonical GObject properties names

GObjectCanonicalPropertiesNames.lua

-- From my other Gist: https://gist.github.com/M1que4s/9f1eec873f87cb02238bd6de2d435705
local lgi     = require("lgi")
local GObject = lgi.require("GObject", "2.0")

local Canonical = GObject.Object:derive("Canonical")

function Canonical:_class_init(Class)
  function Class:set_property(id, val, pspec)
    if id == 1 then self.priv["prop-a"] = val:get_string()
    elseif id == 2 then self.priv["prop-b"] = val:get_string()
    elseif id == 3 then self.priv["prop-c"] = val:get_string()
    elseif id == 4 then self.priv["prop-d"] = val:get_string()
    else GObject.OBJECT_WARN_INVALID_PROPERTY_ID(self, id, pspec) end
  end

  function Class:get_property(id, val, pspec)
    if id == 1 then val:set_string(self.priv["prop-a"])
    elseif id == 2 then val:set_string(self.priv["prop-b"])
    elseif id == 3 then val:set_string(self.priv["prop-c"])
    elseif id == 4 then val:set_string(self.priv["prop-d"])
    else GObject.OBJECT_WARN_INVALID_PROPERTY_ID(self, id, pspec) end
  end

  Class:install_property(1,
    GObject.ParamSpecString(
      "prop-a", "Prop A", "Property A", "A",
      { GObject.ParamFlags.READWRITE, GObject.ParamFlags.CONSTRUCT }
    )
  )

  Class:install_property(2,
    GObject.ParamSpecString(
      "prop-b", "Prop B", "Property B", "B",
      { GObject.ParamFlags.READWRITE, GObject.ParamFlags.CONSTRUCT }
    )
  )

  Class:install_property(3,
    GObject.ParamSpecString(
      "prop-c", "Prop C", "Property C", "C",
      { GObject.ParamFlags.READWRITE, GObject.ParamFlags.CONSTRUCT }
    )
  )

  Class:install_property(4,
    GObject.ParamSpecString(
      "prop-d", "Prop D", "Property D", "D",
      { GObject.ParamFlags.READWRITE, GObject.ParamFlags.CONSTRUCT }
    )
  )
end

--[[ Explanation:

  In the C land, some GObject libraries have clases with properties
  separated by dashes (-), but in other programming languages, that
  isn't a valid name. So... GI (GObject Introspection) based bindings
  (including Vala) commonly translates properties names like this:

    From: example-property
    To: example_property

  Basically replace dashes (-) by underscores (_) and LGI also do
  this in Lua. But... Lua allows use "strange" names in tables and
  since object construction in LGI uses tables, we can use the
  canonical properties names. So... Lets look how can do this:

]]
local o = Canonical({
  ["prop-a"] = "Prop a",
  ["prop-b"] = "Prop b",
  ["prop-c"] = "Prop c",
  ["prop-d"] = "Prop d"
})

-- And, that's it! We're using canonical names in all our code!
print(o["prop-a"])
print(o["prop-b"])
print(o["prop-c"])
print(o["prop-d"])