Ruby's a great language. No - let me rephrase that "Ruby's a fantastic language" ... for many tasks such as "data munging" - handling / manipulating large flows of data, in all sorts of ways. But in my training role, I come across far more people using Ruby on Rails
, Selenium and Watir than Ruby for text handling, so this week I found myself writing a number of new, tuned examples during the private Ruby Course
that I was running. I'm putting many of them onto our web site - the first batch is below - so that my delegates can get back to them, and so that they form a resource for others too.
is one of the standard methods that's inherited from Ruby's basic object, so is available on any object you create. If you simply copy an object through assignment, you're just duplicating its instance variable - i.e. providing another name for the same data, but if you clone it you actually duplicate the contents.
What's the significance? If you simply assign, it's much more efficient ... and any changes you then make are made to both names, which is how you can pass objects into methods and have them modified within. But if you clone, you end up with a distinct additional object that can be modified and manipulated separately; that's a much less common requirement, but it is
needed from time to time.
In Ruby, you can run a function or method by just using its name - there is no need to put a pair of brackets after it as there is in Python to say "run this code". This is good news until you have a variable and a function of the same name, and then the question comes "how does Ruby tell them apart?
The answer is that - where a name has been used for both a variable and a function - that the variable i used if no brackets are given after the name, but the function is run if brackets are used - in other words, it reverts to the Python behavior.
Note also in this example that we can redefine a function in Ruby - the second one simply replaces the first. This is an enabling feature behind mixins, and allows us to come back and modify classes at a later point too.
Ruby, like Perl, has a baffling array of conditional and loop statements and on our courses I like to set one
practical which I ask delegates to complete without using the word "if" or the word "while".
This week, I set a question to ask the delegates to read in the number of course dinners we need to order each day ... with a test to see if the number is in a valid range, a test to see if a special code has been entered to indicate the course has been completed, and a different action to be taken if the number entered is zero.
The simplest possible example of inheritance in Ruby? Almost ... we've defined an animal base class with just a constructor, and then added in two derived classes - Pet and Farm, each with its own constructor. Those have each called the base class constructor so that the common setup code (for name and weight) does not need to be repeated.
Rather than provide separate methods to read values from our objects, we have declared a attr_reader
which allows the variables within the object to be accessed directly. Although such direct variable access is commonly regarded as poor practice in other languages (as it locks the application code to the variable), it is perfectly acceptable in Ruby, where a variable name and a method name are interchangeable, and the class can be later updated if necessary to add logic.
It's surprising how just a few lines of Ruby can make for quite a powerful application. Google's crawler - the Googlebot - visits our web site regularly and indexes our pages, and I wanted to go through our web logs for yesterday and see where it had been, which pages it had checked several times, etc.
This short program also provides a good demonstration of putting many Ruby features together - you'll find string and regular expression matches,arrays and hashes, sorting and various types of looping, and file handling too, all within a simple page of code.
A further Ruby course exercise. Scenario: You have 17 nieces and nephews, and having just won the lottery you are going to distribute $1000.00 between them for Christmas ... or are you?
Little Billy glued your slippers to the floor while you were sleeping in front of the fire one evening, and when you got up, you tripped and stubbed your nose on the fire place. He gets nothing ...
And Jessica, who used to be your favorite, balanced a bucket of water on top of the door and it fell on you and drenched you when you pushed the door open - she gets nothing either
Then there's Jane ...
Create a table showing how many remain in favor, and how much money each will get if you split the money between just those few. (written 2011-02-05, updated 2011-02-10)
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articlesR108 - Ruby - More Classes and Objects 
MTBF of coffee machines - (2005-01-20) 
Think about your design even if you don't use full UML - (2006-03-24) 
What are factory and singleton classes? - (2007-06-04) 
Some Ruby programming examples from our course - (2008-03-21) 
Object Orientation in Ruby - intermediate examples - (2009-07-16) 
Ruby - is_a? v instance_of? - what is the difference? - (2010-01-27) 
Ruby objects - a primer - (2010-01-29) 
Tips for writing a test program (Ruby / Python / Java) - (2010-01-29) 
Defining a static method - Java, Python and Ruby - (2010-02-01) 
Direct access to object variable (attributes) in Ruby - (2010-02-02) 
Object Oriented Ruby - new examples - (2010-02-03) 
The Multiple Inheritance Conundrum, interfaces and mixins - (2010-04-11) 
What is a factory method and why use one? - Example in Ruby - (2010-09-30) 
Ruby - examples of regular expressions, inheritance and polymorphism - (2010-10-02) 
Private and Public - and things between - (2011-01-22) 
Changing a class later on - Ruby - (2011-02-02) 
Ruby - a training example that puts many language elements together to demonstrate the whole - (2011-04-23) 
Why you should use objects even for short data manipulation programs in Ruby - (2012-06-10) 
Private, Protected, Public in Ruby. What about interfaces and abstract classes in Ruby? - (2012-06-23) 
Standard methods available on all objects in Ruby - (2012-06-23) 
Changing what operators do on objects - a comparison across different programming languages - (2014-12-26) 
Where does Ruby load modules from, and how to load from current directory - (2015-06-03) 
Build up classes into applications sharing data types in Ruby - (2015-10-23) 
Testing your new class - first steps with cucumber - (2015-10-23)R104 - Ruby - Control Structures 
1st, 2nd, 3rd revisited in Ruby - (2006-12-02) 
Breaking a loop - Ruby and other languages - (2006-12-03) 
Equality in Ruby - == eql? and equal? - (2006-12-14) 
Ruby's case - no break - (2006-12-17) 
A better alternative to cutting and pasting code - (2007-04-26) 
for loop - how it works (Perl, PHP, Java, C, etc) - (2007-06-06) 
Ruby, C, Java and more - getting out of loops - (2008-03-19) 
Saying NOT in Perl, PHP, Python, Lua ... - (2008-07-04) 
Clean code, jump free (Example in Lua) - (2008-08-06) 
What to do with a huge crop of apples - (2008-11-04) 
Ruby Programming Course - Saturday and Sunday - (2008-11-16) 
Ruby to access web services - (2008-11-16) 
Ruby, Perl, Linux, MySQL - some training notes - (2008-11-23) 
Learning to program in Ruby - examples of the programming basics - (2009-07-15) 
A short form of if ... then ... else - (2009-10-23) 
Passing code to procedures and yield in Ruby - (2010-02-02) 
For loop - checked once, or evety time? Ruby v Perl comparison and contrast - (2010-04-07) 
Alternative loops and conditionals in Ruby and Perl - (2010-07-28) 
Why do I need brackets in Ruby ... or Perl, Python, C or Java - (2010-09-29) 
Splitting data reading code from data processing code - Ruby - (2011-02-04) 
Returning multiple values from a function call in various languages - a comparison - (2011-02-06) 
How a for loop works Java, Perl and other languages - (2011-03-12) 
Is this number between? Does this list include? - Ruby - (2011-04-18) 
Multiple inputs, multiple out, ruby functions - (2011-04-19) 
Does a for loop evaluate its end condition once, or on every iteration? - (2011-08-18) 
Assigning values to variables within other statements - Ruby - (2011-09-07) 
Ruby v Perl - a comparison example - (2012-02-21) 
Finding the total, average, minimum and maximum in a program - (2012-02-22) 
Muttable v immutable and implications - Ruby - (2012-06-20) 
Learning to Program - the conditional statement (if) - (2014-11-21) 
Learning to program - Loop statements such as while - (2014-11-22) 
Conditionals, loops and methods in Ruby - a primer with simple examples - (2014-12-29) 
Finding sum, minimum, maximum and average in Python (and Ruby) - (2015-01-19) 
Separating your code for easier testing, understanding and re-use; example in Ruby - (2015-06-02) 
Alternating valuses / flip-flop / toggle - example in Ruby - (2016-05-17)R050 - Ruby - General 
Ruby Programming and Rails - 4 different courses in one - (2009-03-26) 
Learning PHP, Ruby, Lua and Python - upcoming courses - (2009-06-11) 
Learning to program in ... - (2009-11-15) 
Ruby on Rails - a sample application to teach you how - (2010-01-30) 
Ruby - training for automated testing users - (2010-06-25) 
Ruby - how does it compare and where is it the right language? - (2010-07-11) 
Ruby Documentation through rdoc - (2012-07-07) 
A bright new gem - updated Ruby training - (2014-09-16) 
Back in the saddle again - excellent open source course from Well House Consultants - (2015-11-26)
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