Wrapr

Modify class behavior at runtime. Similar to before/after/around filters in Rails ActionController::Base

Example

require 'wrapr' 
require 'logger'
log = Logger.new(STDOUT)

Wrapr::Wrapr.new(Exception).before(:initialize) do |this,*args|
  log.debug("New exception is being created "+args.inspect)
  args
end

5/0 # we can hijack any class's instance methods and inject our own functionality

Installation

$ gem install wrapr

Potential Uses

Use with ruby-debug to set conditional break points

require 'ruby-debug'
Wrapr::Wrapr.new(Post).before(:find) do |this,*args|
    # Open debug when a post is instantiated 
    # whose attribute "body" contains scrooge
    debugger if args[:body] =~ /scrooge/
    args
end

Wrap existing classes in logging functionality Mirror object modifications?, if there were no such this as :after_save

# given there is a post class in active record

w = Wrapr::Wrapr.new(Post)
w.after(:save) do |this,*args|
  if this.new?
    SomeAlternateDatabaseModel.new(this.attributes).save 
  else
    SomeAlternateDatabaseModel.find(this.id).update_attributes(this.attributes)
  end
end

Tested Versions

• ruby-1.9.2,
• ruby-1.8.7
• jruby-1.6.4