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 Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own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)) |
Changing a class later on - Ruby
In Ruby, you can define a class ... and then come back and add methods to it. But why would you want to?
Let's suppose that you've got a base class - I'll use "Rectangle" as my example, and you've already subclassed it to "Square" and perhaps a few other things, via a required file that you share between a number of programs. Then you want to use that group of classes in a new application, but with a modification to one of the base methods. The example I used during yesterday's course was that the rectangles were pictures, and I wanted to add a frame, 1 unit wide, around them in my new code. [full source].
Well - given that scenario, you've got an excellent excuse for going back within your own code and replacing the methods of Rectangle that are changed when you add a frame, and it'll be the new routines that are run when you call methods in the already-defined subclasses. It's very neat indeed, and the alternative would be ugly.
(written 2011-02-02)
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles R108 - Ruby - More Classes and Objects [184] MTBF of coffee machines - (2005-01-20) [656] Think about your design even if you don't use full UML - (2006-03-24) [1217] What are factory and singleton classes? - (2007-06-04) [1587] Some Ruby programming examples from our course - (2008-03-21) [2292] Object Orientation in Ruby - intermediate examples - (2009-07-16) [2601] Ruby - is_a? v instance_of? - what is the difference? - (2010-01-27) [2603] Ruby objects - a primer - (2010-01-29) [2604] Tips for writing a test program (Ruby / Python / Java) - (2010-01-29) [2616] Defining a static method - Java, Python and Ruby - (2010-02-01) [2620] Direct access to object variable (attributes) in Ruby - (2010-02-02) [2623] Object Oriented Ruby - new examples - (2010-02-03) [2717] The Multiple Inheritance Conundrum, interfaces and mixins - (2010-04-11) [2977] What is a factory method and why use one? - Example in Ruby - (2010-09-30) [2980] Ruby - examples of regular expressions, inheritance and polymorphism - (2010-10-02) [3142] Private and Public - and things between - (2011-01-22) [3158] Ruby training - some fresh examples for string handling applications - (2011-02-05) [3260] Ruby - a training example that puts many language elements together to demonstrate the whole - (2011-04-23) [3760] Why you should use objects even for short data manipulation programs in Ruby - (2012-06-10) [3781] Private, Protected, Public in Ruby. What about interfaces and abstract classes in Ruby? - (2012-06-23) [3782] Standard methods available on all objects in Ruby - (2012-06-23) [4366] Changing what operators do on objects - a comparison across different programming languages - (2014-12-26) [4504] Where does Ruby load modules from, and how to load from current directory - (2015-06-03) [4550] Build up classes into applications sharing data types in Ruby - (2015-10-23) [4551] Testing your new class - first steps with cucumber - (2015-10-23)
Some other Articles
A new monopoly on the ferry to Northern IrelandSplitting data reading code from data processing code - RubyRake - a build system using code written in RubyChanging a class later on - RubyPoints West to BelfastJargon bustingDisassembling Python and Java - previously compiled codePython dictionaries - mutable and immutable keys and valuesLooking back at www.wellho.net
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