h1. Context-oriented Programming in Ruby

h1. → 'contextr'


h2. What

TODO

h2. Installing

Nothing more than typing

<pre syntax="ruby">sudo gem install contextr</pre>

h2. The basics

In your code use 

<pre syntax="ruby">require 'rubygems'
require 'contextr'</pre>

and ContextR will be ready to use.

h2. Demonstration of usage

<pre syntax="ruby">
require "rubygems"
require "contextr" 

class Person
  attr_accessor :name, :address, :university

  def initialize name, address, university
    self.name = name
    self.address = address
    self.university = university
  end

  def to_s
    "Name: #{name}"
  end
end

class University
  attr_accessor :name, :address

  def initialize name, address
    self.name = name
    self.address = address
  end

  def to_s
    "Name: #{name}"
  end
end

class Person
  layer :address, :education

  address.post :to_s do | n |
    n.return_value += "; Address: #{address}"
  end

  education.post :to_s do | n |
    n.return_value += ";\n[Education] #{university}"
  end
end

class University
  layer :address

  address.post :to_s do | n |
    n.return_value += "; Address: #{address}"
  end
end


hpi = University.new( "Hasso-Plattner-Institut", "Potsdam" )
somePerson = Person.new( "Gregor Schmidt", "Berlin", hpi )

puts 
puts somePerson
ContextR::with_layers :education do
  puts 
  puts somePerson

  ContextR::with_layers :address do
    puts 
    puts somePerson

    ContextR::without_layers :education do
      puts 
      puts somePerson
    end
  end
end
puts 
</pre>
The above code prints:

<pre>
Name: Gregor Schmidt

Name: Gregor Schmidt;
[Education] Name: Hasso-Plattner-Institut

Name: Gregor Schmidt; Address: Berlin;
[Education] Name: Hasso-Plattner-Institut; Address: Potsdam

Name: Gregor Schmidt; Address: Berlin
</pre>

You may find other examples in the <code>examples</code> folder.

h2. Other resources

* "Rubyforge Project Page":http://rubyforge.org/projects/contextr
* "Author's Development Blog - The Ruby Ahead":http://www.nach-vorne.de
* "ContextR Statistics on ohloh":http://www.ohloh.net/projects/5037

h2. License

This code is free to use under the same terms as Ruby 

h2. Contact

Comments are welcome. Send an email to "Gregor Schmidt":mailto:ruby@schmidtwisser.de