4. Extending a Class

Having the ability to extend a class gives more potential for code reusability and more. The example below shows how we can extend our Logger class created in the previous page:

local BetterLogger = Class():Extends(Logger) --Starts the definition of a Class and makes it extend Logger.

function BetterLogger:New(class) --Override the default constructor.
    self.name = class.__name
end

local getTimestamp = _G.os.time
local formatTimestamp = _G.os.date

local function getTimeString() --"Private" method to get the current time as a string.
    return formatTimestamp("%H:%M:%S", getTimestamp())
end

local print = _G.print

function BetterLogger:Log(msg) --A public method to extend the functionality of the superclass' method.
    self.__super.Log(self, ("[%s %s] %s"):format(getTimeString(), self.name, msg))
end

return BetterLogger

When extending a class, as seen above, the class being extended gains access to the super class via self.__super, which allows the original implementation of a method to be called.