I've spent a lot of the weekend working on our Lua course ... and for those of you new to this language I'll be sharing a few snippets with you here on "The Horse's Mouth" over coming weeks. Today, I've got a short section which starts to introduce how you can do OO programming in Lua. The section of notes goes on to cover all the OO classics such as Encapsulation, Polymorphism and Inheritance and the course examples for this module are online via here

In Lua, we can keep functions in a table too, and we can bind a series of "metamethods" to a table which give it additional properties We also have syntactic sugar to make the new structures look and run sweetly. All of which leads to an effective Object Oriented capability in Lua, although without the classic keywords "class", "method", "private" etc.

Here are some of the basics - the use of the "." operator, and the storage of a piece of code as a first class function alongside the data.

stuff = {}
 
stuff["john"] = 14
stuff.dick = 24
function stuff.henry(value)
  return value * 2
  end
 
print (stuff.john)
print (stuff["dick"])
print (stuff.henry(16))
 
print (stuff["john"])

If you're trying to work out the difference between the "." operator and the use of a subscript in square brackets ... don't. They mean the same thing!

Here's how that program runs:

[trainee@easterton u107]$ lua dibdab
14
24
32
14
24
34
[trainee@easterton u107]$
(written 2008-06-30)

 U107 - Object Orientation - the Lua way
  [1699] If you are learning Lua, here are some more examples - (2008-07-06)
  [1743] First class functions in Lua lead to powerful OO facilities - (2008-08-07)
  [1819] Calling base class constructors - (2008-10-03)
  [2318] For Lua Programmers AND for Town Planners - (2009-08-02)
  [2359] A fresh example - objects the Lua way - (2009-08-13)
  [2455] Lua examples - coroutines, error handling, objects, etc - (2009-10-15)
  [2701] Is Lua an Object Oriented language? - (2010-04-01)
  [2703] Lua Metatables - (2010-04-02)
  [2710] __index and __newindex in Lua - metatable methods - (2010-04-05)
  [3142] Private and Public - and things between - (2011-01-22)
  [3396] Tables as Objects in Lua - a gentle introduction to data driven programming - (2011-08-17)
  [3524] Metaclasses (Python) and Metatables (Lua) - (2011-11-17)
  [3683] Weak references in Lua - what are they, and why use them? - (2012-04-04)
  [3694] Special __ methods you can use in Lua metatables - (2012-04-12)
  [3727] Using Lua tables as objects - (2012-05-11)
  [3730] What is a metatable? How do I set one up? How do I use them? Lua - (2012-05-12)
  [4117] Is Lua an Object Oriented language? - (2013-06-15)
  [4248] Metatables, Metamethods, classes and objects in Lua - (2014-03-18)
  [4273] Dot or Colon separator between table name and member in Lua - what is the difference? - (2014-05-06)
  [4572] Tables with values and code in Lua - looks like an object? - (2015-11-05)
  [4573] Classic style OO code - in Lua - (2015-11-05)
  [4753] Lua, Tcl, Python, C and C++ courses - at our Melksham HQ or on your site - forward from July 2017 - (2017-07-02)

Back to Co-routines in Lua - co-operative processing

Previous and next or Horse's mouth home

Forward to July to December 2008 - Open Source training schedule

Saying NOT in Perl, PHP, Python, Lua ...
Lua Course - here is the index
Defensive coding techniques in PHP?
July to December 2008 - Open Source training schedule
Towards Object Oriented Programming in Lua
Co-routines in Lua - co-operative processing
Conversion of c/r line ends to l/f line ends
Some sideways thoughts on the news
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