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Perl design patterns example

For short programs, just a few lines of code in a single block do an excellent job. As the program size increases, some sort of structure such as named blocks of code (sub, def, function, proc, lambda etc) becomes logical. And as the code grows further, you should consider splitting out logic relating to a particular data type into a class of methods, with each class having its own test harness.

There's a parallel here in real life writing - a tweet is a single block. Posts to social media such as facebook will be a series of paragraphs. And technical articles will be a series of linked pages.

Python - being an object oriented language - is designed around the larger coding model. And that larger coding model is very common in these days of shared code between a lot of smaller projects; that's why Python is especially popular. But you can also write excellent Object Oriented code in Perl to conform to the same principles, and give you the same benefits of unit testability and code re-usability. And that's something we cover on our Perl for Larger Projects course which is running this week.

Yesterday, we covered OO as implemented in Perl, statring from first principles. And during the day I built up to a complete example - [here] - showing object definition and inheritance, and moving on to look at patterns for generic property accessors through get and set methods, and also through the autoloader. The example also includes factory and comparator design patterns which you're welcome to look at, copy, adopt... or come on the course next time to learn in more depth.
(written 2013-05-20, updated 2013-05-25)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
P218 - Perl - More Objects
  [4366] Changing what operators do on objects - a comparison across different programming languages - (2014-12-26)
  [4356] Object factories in C++, Python, PHP and Perl - (2014-12-19)
  [4098] Using object orientation for non-physical objects - (2013-05-22)
  [3941] Building an object based on another object in Perl - (2012-12-03)
  [3581] Perl - calls to methods that use => - what do they mean? - (2012-01-16)
  [3377] What do I mean when I add things in Perl? - (2011-08-02)
  [3098] Learning Object Orientation in Perl through bananas and perhaps Moose - (2010-12-21)
  [3097] Making Perl class definitions more conventional and shorter - (2010-12-20)
  [2972] Some more advanced Perl examples from a recent course - (2010-09-27)
  [2876] Different perl examples - some corners I rarely explore - (2010-07-18)
  [2811] Igloos melt in the summer, but houses do not - (2010-06-15)
  [2717] The Multiple Inheritance Conundrum, interfaces and mixins - (2010-04-11)
  [2651] Calculation within objects - early, last minute, or cached? - (2010-02-26)
  [2427] Operator overloading - redefining addition and other Perl tricks - (2009-09-27)
  [1949] Nuclear Physics comes to our web site - (2008-12-17)
  [1819] Calling base class constructors - (2008-10-03)
  [1665] Factory method example - Perl - (2008-06-04)
  [1664] Example of OO in Perl - (2008-06-03)
  [1435] Object Oriented Programming in Perl - Course - (2007-11-18)
  [1320] Perl for Larger Projects - Object Oriented Perl - (2007-08-25)
  [1217] What are factory and singleton classes? - (2007-06-04)
  [930] -> , >= and => in Perl - (2006-11-18)
  [831] Comparison of Object Oriented Philosophy - Python, Java, C++, Perl - (2006-08-13)
  [656] Think about your design even if you don't use full UML - (2006-03-24)
  [592] NOT Gone phishing - (2006-02-05)
  [588] Changing @INC - where Perl loads its modules - (2006-02-02)
  [531] Packages in packages in Perl - (2005-12-16)
  [246] When to bless a Perl variable - (2005-03-15)
  [227] Bellringing and Programming and Objects and Perl - (2005-02-25)

Q908 - Object Orientation and General technical topics - Object Orientation: Design Patterns
  [4673] Separating detailed data code from the main application - Ruby example - (2016-05-16)
  [4663] Easy data to object mapping (csv and Python) - (2016-03-24)
  [4626] Singleton design pattern - examples and uses - (2016-01-20)
  [4581] Thin application, thick objects - keep you main code simple. Example in Ruby - (2015-11-21)
  [4421] How healthy are the stars of stage and screen? - (2015-02-09)
  [4396] Java Utility class - flexible replacement for array. Also cacheing in objects and multiple catch clauses example. - (2015-01-16)
  [4377] Designing a base class and subclasses, and their extension, in C++ - (2015-01-01)
  [4359] How to avoid too many recalculations within an object - (2014-12-21)
  [4330] Java - factory method, encapsulation, hashmap example - (2014-11-27)
  [4325] Learning to program - what are algorithms and design patterns? - (2014-11-22)
  [4021] Spike solution, refactored and reusable, Python - Example - (2013-02-28)
  [3843] Caching Design Patterns - (2012-08-20)
  [3810] Reading files, and using factories to create vectors of objects from the data in C++ - (2012-07-21)
  [3716] Learning C++ - a design pattern for your first class - (2012-05-02)
  [3608] Design Patterns - what are they? Why use them? - (2012-02-12)
  [2977] What is a factory method and why use one? - Example in Ruby - (2010-09-30)
  [2741] What is a factory? - (2010-04-26)
  [2322] Looking for a practical standards course - (2009-08-05)
  [1224] Object Relation Mapping (ORM) - (2007-06-09)
  [485] North, Norther and Northest - PHP 5 Objects - (2005-11-04)


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Melksham Chamber of Commerce - Report for AGM, 21st May 2013
Perl design patterns example
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Identity in Python
A reminder of why we opened Well House Manor for our customers
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This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

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