Home Accessibility Courses Twitter The Mouth Facebook Resources Site Map About Us Contact
Python, Lua and Tcl - public course schedule [here]
Private courses on your site - see [here]
Please ask about maintenance training for Perl, PHP, Java, C, C++, Ruby, MySQL and Linux / Tomcat systems
Adding user methods via a metatable
Object Orientation - the Lua way example from a Well House Consultants training course
More on Object Orientation - the Lua way [link]

This example is described in the following article(s):
   • Lua Metatables - [link]

This example references the following resources:

Source code: metamid Module: U107

-- ================ "Class" definition stuff
pet = pet or {}
metapet = metapet or {}

function pet.new(breed,weight,age)
        current = {}
        -- first example use different name
        -- to show the mechanism
        current.type = breed
        -- then save the need for a thesaurus
        current.weight = weight
        current.age = age

        -- Add any common "pet" stuff into the
        -- newly created table current
        return current

-- Define common functionallity

-- See http://lua-users.org/wiki/MetatableEvents
-- for a listing of all the specials that you
-- can use

function metapet.__tostring(self)
        result = "A pet of type " ..
                self.type .. " aged " ..
                self.age .. " weighing " ..
        return result

-- Unrecognised member being called
-- the __index function will return a pointer
-- to the correct piece of code
function metapet.__index(self, method)
        if method == "getliftable" then
                return metapet.getliftable
        return nil

function metapet.getliftable(this)
        if this.weight < 30 then
                return true
                return nil

-- ================ Calling stuff

gypsy = pet.new("dog",28,3)
charles = pet.new("prince",95,60)
family = {gypsy, charles}

for _,v in ipairs(family) do
        print (v)
        if v:getliftable() then
                print ("Can lift ")
                print ("is very heavy")

Learn about this subject
This module and example are covered on the following public courses:
 * Learning to program in Lua
 * Lua Programming
 * Lua Programming
Also available on on site courses for larger groups

Books covering this topic
Yes. We have over 700 books in our library. Books covering Lua are listed here and when you've selected a relevant book we'll link you on to Amazon to order.

Other Examples
This example comes from our "Object Orientation - the Lua way" training module. You'll find a description of the topic and some other closely related examples on the "Object Orientation - the Lua way" module index page.

Full description of the source code
You can learn more about this example on the training courses listed on this page, on which you'll be given a full set of training notes.

Many other training modules are available for download (for limited use) from our download centre under an Open Training Notes License.

Other resources
• Our Solutions centre provides a number of longer technical articles.
• Our Opentalk forum archive provides a question and answer centre.
The Horse's mouth provides a daily tip or thought.
• Further resources are available via the resources centre.
• All of these resources can be searched through through our search engine
• And there's a global index here.

Web site author
This web site is written and maintained by Well House Consultants.

Purpose of this website
This is a sample program, class demonstration or answer from a training course. It's main purpose is to provide an after-course service to customers who have attended our public private or on site courses, but the examples are made generally available under conditions described below.

Conditions of use
Past attendees on our training courses are welcome to use individual examples in the course of their programming, but must check the examples they use to ensure that they are suitable for their job. Remember that some of our examples show you how not to do things - check in your notes. Well House Consultants take no responsibility for the suitability of these example programs to customer's needs.

This program is copyright Well House Consultants Ltd. You are forbidden from using it for running your own training courses without our prior written permission. See our page on courseware provision for more details.

Any of our images within this code may NOT be reused on a public URL without our prior permission. For Bona Fide personal use, we will often grant you permission provided that you provide a link back. Commercial use on a website will incur a license fee for each image used - details on request.

You can Add a comment or ranking to this page

© WELL HOUSE CONSULTANTS LTD., 2018: Well House Manor • 48 Spa Road • Melksham, Wiltshire • United Kingdom • SN12 7NY
PH: 01144 1225 708225 • FAX: 01144 1225 793803 • EMAIL: info@wellho.net • WEB: http://www.wellho.net • SKYPE: wellho

PAGE: http://www.wellho.net/resources/ex.php4 • PAGE BUILT: Sun Jan 31 13:04:01 2016 • BUILD SYSTEM: WomanWithCat