Introducing Ruby


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Basic introduction to the history and uses of the Ruby programming lanaguage.

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  • * A dynamic object-oriented programming language
    * Inspired by Perl, Eiffel, Ada, Lisp and Smalltalk.
    * Its creator stated his goal was to "make Ruby natural, not simple."

    Ruby is a very powerful language that is also very flexible. It is pervasively
    object-oriented. It is a general purpose language, so it is useful in the same
    places that Perl, PHP, etc. would be used.
  • Developed by Yukihiro "matz" Matsumoto in 1993 with its first public
    release in Japan in 1995.

    It saw its first English announcement in 1998 and
    was followed by the publication of the Programming Ruby book in 2000 by Dave
    Thomas and Andy Hunt.

    The second edition of Programming Ruby, known as the
    "Pickaxe Book" was released in 2004.
  • The Ruby world is transitioning to 1.9 and most major and currently maintained
    projects have made the switch to supporting 1.9. The community is tracking the
    progress of this transition with relation to Gems as

    Beyond the "official" interpreter, usually referred to as "MRI," there are a
    number of projects to develop alternative interpreters for various reasons and
    to met various needs.

    * Enterprise: Ruby 1.8 with better memory handling and other performance optimizations
    * JRuby: Ruby on top of the JVM, fastest 1.8 implementation around.
    * MacRuby: Ruby on top of Apple's Objective-C runtime.
    * IronRuby: Ruby on top of the .NET DLR.
    * Rubinius: Ruby developed with a tight C++ main interpreter and most of the rest of the language developed the Ruby subset understood by the main interpreter.
  • If you are on Windows you should use Cygwin. Or, better yet, move to a unix
    environment since many of the best and most useful Ruby Gems use C extensions
    which are a pain to get working outside of a unix environment. There is the
    one-click installer as well, but it is badly outdated, and the straight binary
    releases from

    For Linux you can use your favorite package manager to install ruby, irb and
    rdoc to get the whole base system. Some distros are starting to make 1.9
    available but it usually has a suffix on all the commands which make them
    more cumbersome.

    For OS X if you have Leopard you already have Ruby available but if you use
    MacPorts you can get the latest version and even 1.9 with no suffix. Mac users
    also have access to the MacRuby project which is very promising and should
    eventually make OS X an even better platform for Rubyists.

    If you don't want to install Ruby you can play with an online interactive
    environment at
  • Ruby's command set provides a rich set of features for exploring the language,
    its documentation and different ways of using it.
  • Ruby has a number of conventions which are collectively referred to as the
    "Ruby Way."

    You are free to ignore these conventions if you like, but don't expect much
    love from your fellow Rubyists. And you can expect a nasty warning from the
    interpreter if you fiddle with what it expects of a constant, although you are
    actually free to change a constant.

    Module and Class names are actually constants which is why some consider it acceptable to use camel case for constants as well.
  • One big thing to understand from the start with Ruby is that everything is an

    With the exception of reserved keywords everything is an object in Ruby. This
    allows for really interesting programming techniques in terms of chaining
    method invocation and even manipulation of parameters.

    Object is the parent of all classes.

    Duck typing is the pattern Ruby follows where behavior is closely coupled to type.
  • Another big thing in Ruby are symbols. Because of Ruby's object model two
    strings which have the same character sequences are not the same. They have
    different object ids and occupy separate places in memory. Some have described
    symbols as immutable strings but this is really an oversimplification.

    Used with hashes for keys and as pseudo-constants.

    There is a lot more to symbols and whole blogs have focused on uses for
    symbols so go Google Ruby symbols if you want to learn more.
  • If you are working with a class you have two special kinds of variables
    available to you. Instance variables are unique to a particular instance of an
    object while class variables are unique to all instances of a given class.
  • Strings are really straight forward. Ruby supports single and double quoted
    strings, as well as HEREDOC style strings and alternative encapsulated
    strings. Strings also support interpolation of variables as well.

    Escaped new lines are optional when using certain ruby methods. Most of the
    time you don't need to be explicit with new lines, Ruby uses them where you
    would expect automatically.
  • Ruby deals well with integers and floating point values as you would expect.
    It supports decimal and scientific notation as well as hex and octal.
  • Something that is missing that some may wonder about is an explicit return. In
    Ruby the last expression within a method is returned as the result of the
    method by default. So explicit returns are not needed. You can do an explicit
    return however.
  • A thing to note about Ruby classes is that they only support single
    inheritance, although there is an inheritance hierarchy at work in Ruby.
    Inheritance is also pretty straightforward to achieve.
  • The way you call the constructor is by using the new method. To define a
    constructor for a class just define a method called initialize.
  • You can also define attributes for classes. These are just set/get accessors
    for the class, if defined they are usually tied to an instance variable.
  • You can invoke any inherited methods by calling super().
  • Modules are collections of methods and constants. They are used to achieve
    much the same ends as multiple inheritance would provide but without the
  • Modules get mixed in to classes using the include method.
  • Something you should have noticed if you were following along with the code
    examples in irb is that I didn't redefine the entire class every time I did
    something new. One of the most useful and potentially troublesome features of
    Ruby is the open nature of classes and modules. You can just open them up and
    add to them. Heck, there are even ways to remove methods and the like. Here's
    an example of a modification to the way numbers work in Ruby.

    You can add and redefine methods on any class or module very easily in Ruby.
    Again, this is a very powerful but also dangerous capability.
  • Ruby has all the typical control structures and some of its own interesting ones.

    That last one is a fun way to work with collections like arrays or hashes.
  • Ruby has all the types you would expect from a good dynamic language. Most
    we've already discussed but here's a quick rundown of the standard ones,
    including some we didn't talk about.
  • Ruby supports closures in the forms of blocks, procs and lambdas. Blocks are
    basically pieces of code that you can pass as arguments to method calls. We
    saw a basic block with control structures.

    You can think of blocks like anonymous methods that are able to capture the
    context they are called in. Procs are essentially blocks that have been stored
    in a variable. This allows a the Proc to be more reusable than a block and
    allows the developer to avoid repetition.

    Ruby also provides lambdas which are similar to Procs but check the number of
    variables passed to them. For more on these three special structures in Ruby
    you can Google them and learn all the different ways they can be used.
  • The best way to think of RubyGems is to think of it like CPAN for Ruby. It is
    the de facto standard for distributing reusable Ruby code. Lots of libraries,
    and most Ruby applications are distributed as Gems.

    You can get RubyGems either by default with Ruby 1.9 or downloaded from But lets look at how you use RubyGems a little bit. Many Linux distros also have it available as a package.
  • When compared to the package repositories of other popular languages Ruby is
    definitely a productive community. The numbers for Github may give a slightly
    exaggerated impression since many of the gems hosted with them are duplicates
    of gems distributed through Rubyforge or are unstable development packages.

    However, it is clear that Ruby is a healthy community of users sharing their
    work with one another.
  • Introducing Ruby

    2. 2. WHO IS THIS GUY? James Thompson @plainprogrammer Web Administrator & Student @ New Orleans Baptist Theological Seminary
    3. 3. WHAT IS RUBY? Ruby is a dynamic, open source programming language with a focus on simplicity and productivity –
    4. 4. HISTORY Created by Yukihiro “matz” Matsumoto Started development in 1993 First public release in 1995 (Japan) First English release in 1998 “make Ruby natural, not simple.”
    5. 5. CURRENT STATE Legacy Stable: 1.8.7p72 Current Stable: 1.9.1p129 A community in transition Alternatives to MRI
    6. 6. INSTALLING RUBY •Windows: Cygwin is the best option. One-click installer available but out of date. •Linux: apt-get install ruby rdoc irb •OS X: Already installed in 10.5. Available through MacPorts as well.
    8. 8. RUBY’S COMMANDS •ruby main interpreter •irb interactive ruby shell •ri ruby information, manpages for classes •rdoc ruby documentation compiler •erb ruby templating system
    9. 9. RUBY CONVENTIONS •variable_name •method_name •ClassName •ModuleName •ConstantName | CONTSTANT_NAME
    10. 10. RUBY SYNTAX
    11. 11. OBJECT ORIENTATION 5.class #=> Fixnum In ruby everything is an object. 3.9.class #=> Float "Hello".class #=> String Fixnum.class #=> Class This is both powerful and nil.class #=> NilClass different.
    12. 12. SYMBOLS :a_symbol opts = { :a_key => "Some value!", :another_key => "another value..." }
    13. 13. INSTANCE & CLASS VARIABLES @instance_variable @@class_variable
    14. 14. STRINGS name = 'BarCamp Joe' greeting = "Hello, #{name}!" long_greeting <<-EOS Hello my old friend, #{name}! How have you been? EOS alternate_greeting = %{G'day, #{name.upcase}!}
    15. 15. NUMBERS a = 1 b = 2.0 c = 2.3e5 d = 0x3F e = 0244
    16. 16. METHODS def say_hello(name) result = "Hello, #{name}!" end puts say_hello("BarCamp NOLA")
    17. 17. METHODS def say_hello(name) result = "Hello, #{name}" return result end puts say_hello("BarCamp NOLA")
    18. 18. CLASSES class Greeter def say_hello(name) puts "Hello, #{name}!" end end doorman = doorman.say_hello("BarCampers")
    19. 19. CLASSES class RudeGreeter < Greeter def say_hello(name) puts "" end end
    20. 20. CLASSES class Greeter def initialize(name) @greeters_name = name end end
    21. 21. CLASSES class Greeter attr_reader :name end
    22. 22. CLASSES class RudeGreeter < Greeter def initialize(name, rudeness) @rudeness = rudeness super(name) end end
    23. 23. MODULES module Farewell def bid_farewell(name) "Good bye, #{name}!" end end
    24. 24. MODULES class Greeter include Farewell end doorman ="John") doorman.bid_farewell("BarCampers")
    25. 25. CLASS/MODULE MUTABILITY class Numeric def plus(n) self.+(n) end end y = 6 #=> 11
    26. 26. CONTROL STRUCTURES if "a" == "a" puts "a" end unless "a".nil? puts "a" end puts "a" unless "a".nil? name = case when num == 1: "one" when num == 2: "two" else num.to_s end [1,2,3].each do |value| puts value.to_s end
    27. 27. TYPES •Numbers •Strings •Regular Expressions (/^(foo|bar)+$/) •Arrays ([1,2,3]) •Hashes •Ranges (1..10, "a"..."z") •Symbols
    28. 28. BLOCKS, PROCS & LAMBDAS [1,2,3].each do |value| puts value.to_s end square = do |n| n ** 2 end
    29. 29. RUBYGEMS
    30. 30. CPAN Pear PECL RAA Rubyforge Github PyPI 17,000 12,750 8,500 4,250 Obsolete 0 Perl Ruby Python PHP PERL, PHP & RUBY PACKAGES
    31. 31. SEEING WHAT’S OUT THERE gem list --remote gem list
    32. 32. GETTING HELP gem help gem help commands
    33. 33. INSTALLING GEMS gem install rails gem install mysql sqlite3-ruby gem install rails --no-ri --no-rdoc
    34. 34. COMMANDS FOR GEMS rails --version
    35. 35. REMOVING GEMS gem uninstall mysql
    36. 36. WHY USE RUBY?
    37. 37. QUESTIONS?
    38. 38. MORE RESOURCES