A fresh example - objects the Lua way
One of the requirements we often have in our web server log file analyses is to connect together a series of accesses from a single IP address into a "visit", and this formed an example on Tuesday's Lua course.
In Lua, you can overload (i.e. redefine) operators so that they work differently on tables of different types, and in this case I chose to redefine addition so that it concatenates two visits, allowing all the access log records from a single source to be logically grouped even though there are many different visitors (i.e. IP addresses) coming to our site at the same time:
(This diagram shows you just how wide ranging our visitors are - it's dynamic, showing you the last 15 minutes up to when you loaded the page!)
The log file analysis program comes several days into our Lua Programming course
so it's not practical for me to document every line here, but if you already know Lua, you're more than welcome to look at the calling code here
and the object definition here
. The latter contains a good block of comments! (written 2009-08-13)
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articlesU107 - Object Orientation - the Lua way 
Is Lua an Object Oriented language? - (2013-06-15) 
What is a metatable? How do I set one up? How do I use them? Lua - (2012-05-12) 
Using Lua tables as objects - (2012-05-11) 
Special __ methods you can use in Lua metatables - (2012-04-12) 
Weak references in Lua - what are they, and why use them? - (2012-04-04) 
Metaclasses (Python) and Metatables (Lua) - (2011-11-17) 
Tables as Objects in Lua - a gentle introduction to data driven programming - (2011-08-17) 
Private and Public - and things between - (2011-01-22) 
__index and __newindex in Lua - metatable methods - (2010-04-05) 
Lua Metatables - (2010-04-02) 
Is Lua an Object Oriented language? - (2010-04-01) 
Lua examples - coroutines, error handling, objects, etc - (2009-10-15) 
For Lua Programmers AND for Town Planners - (2009-08-02) 
Calling base class constructors - (2008-10-03) 
First class functions in Lua lead to powerful OO facilities - (2008-08-07) 
If you are learning Lua, here are some more examples - (2008-07-06) 
Towards Object Oriented Programming in Lua - (2008-06-30)
Some other Articles
Alpaca Case or Camel CaseThornham Farm Shop, Seend Cleeve, nr MelkshamGeocoding - converting address to latitude / Longitude with PHP via GoogleError Handling in Lua with assert and pcallA fresh example - objects the Lua wayEncapsulating shared code in a Lua moduleChecking if the user has entered a number (Lua)Passing multiple results back from a function - Lua, Python, etcSee this page in FrenchTraining, Open Source computer languages
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