Learning Object Orientation in Perl through bananas and perhaps Moose

For 2023 (and 2024 ...) - we are now fully retired from IT training.
We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.

Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!

I am also active in many other area and still look after a lot of web sites - you can find an index ((here))

Perl has the most incredbible range of OO facilities (though at times it's overfeatured and a bit old fashioned / tricky to use). So yesterday I wrote a whole series of examples ... and then went on to explore Moose - a module which adds extra keywords and lets you define your classes in a shorter and somewhat more conventional way. See [here] for the moose series - this post introduces the standard facilities in a series of examples.

Bananas.

Our supplier for the hotel provides three types - best bananas, large bananas and small bananas ... "best" are priced per kg, "large" per fruit, and "small" per bunch ... which makes life interesting when we do stock controls and start looking at supply usage, but it did provide a very useful example for yesterday ...

Here are the examples

Setting up a package of hash references - [source]

How to bless the references and thus turn them into objects - [source] - First practical example

Notifying the caller of where errors are triggered in his code via carp, croak and confess - [source]

Use of the caller function to examine the stack frames - [source]

Base class, subclasses, inheritance - [source] First example that shows how we do polymorphism in Perl

How we can use the Universal superclass to find out what our object is / what it can do - [source] can lead to poor class design!

A factory method to construct objects indirectly - [source]

Perl 5's OO facilities are covered on our Perl for Larger Projects course - where we cover OO principles too as necessary. Moose can be introduced on private courses (it's a bit of an interim thing prior to Perl 6 though), or if you're on the public course let me know you would like to cover it and I'll run an extra session one evening.

(written 2010-12-21)

Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles

P310 - Perl - Moose
  [3097] Making Perl class definitions more conventional and shorter - (2010-12-20)

P218 - Perl - More Objects
  [227] Bellringing and Programming and Objects and Perl - (2005-02-25)
  [246] When to bless a Perl variable - (2005-03-15)
  [531] Packages in packages in Perl - (2005-12-16)
  [588] Changing @INC - where Perl loads its modules - (2006-02-02)
  [592] NOT Gone phishing - (2006-02-05)
  [656] Think about your design even if you don't use full UML - (2006-03-24)
  [831] Comparison of Object Oriented Philosophy - Python, Java, C++, Perl - (2006-08-13)
  [930] -> , >= and => in Perl - (2006-11-18)
  [1217] What are factory and singleton classes? - (2007-06-04)
  [1320] Perl for Larger Projects - Object Oriented Perl - (2007-08-25)
  [1435] Object Oriented Programming in Perl - Course - (2007-11-18)
  [1664] Example of OO in Perl - (2008-06-03)
  [1665] Factory method example - Perl - (2008-06-04)
  [1819] Calling base class constructors - (2008-10-03)
  [1949] Nuclear Physics comes to our web site - (2008-12-17)
  [2427] Operator overloading - redefining addition and other Perl tricks - (2009-09-27)
  [2651] Calculation within objects - early, last minute, or cached? - (2010-02-26)
  [2717] The Multiple Inheritance Conundrum, interfaces and mixins - (2010-04-11)
  [2811] Igloos melt in the summer, but houses do not - (2010-06-15)
  [2876] Different perl examples - some corners I rarely explore - (2010-07-18)
  [2972] Some more advanced Perl examples from a recent course - (2010-09-27)
  [3377] What do I mean when I add things in Perl? - (2011-08-02)
  [3581] Perl - calls to methods that use => - what do they mean? - (2012-01-16)
  [3941] Building an object based on another object in Perl - (2012-12-03)
  [4096] Perl design patterns example - (2013-05-20)
  [4098] Using object orientation for non-physical objects - (2013-05-22)
  [4356] Object factories in C++, Python, PHP and Perl - (2014-12-19)
  [4366] Changing what operators do on objects - a comparison across different programming languages - (2014-12-26)

P213 - Perl - Creating your own Classes
  [975] Answering ALL the delegate's Perl questions - (2006-12-09)
  [983] Blessing in Perl / Member variable in Ruby - (2006-12-14)
  [1864] Object Oriented Perl - First Steps - (2008-11-01)
  [1925] Introduction to Object Oriented Programming - (2008-12-06)
  [2169] When should I use OO techniques? - (2009-05-11)
  [2834] Teaching examples in Perl - third and final part - (2010-06-27)
  [2877] Further more advanced Perl examples - (2010-07-19)
  [2969] What does blessing a variable in Perl mean? - (2010-09-24)
  [3059] Object Orientation in an hour and other Perl Lectures - (2010-11-18)
  [3833] Learning to use existing classes in Perl - (2012-08-10)
  [4607] Classes and object - first steps in Perl 6 - (2016-01-02)

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Some other Articles

AND and OR operators - what is the difference between logical and bitwise varieties?
The week before Christmas
Looking ahead and behind in Regular Expressions - double matching
Perl - database access - DBD, DBI and DBIx modules
Learning Object Orientation in Perl through bananas and perhaps Moose
Contrast in pictures
The Christmas Season has arrived
Setting your user_agent in PHP - telling back servers who you are
How many toilet rolls - hotel inventory and useage

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