11b-refinements.ipynb

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  {
   "cells": [
    {
     "cell_type": "heading",
     "level": 1,
     "metadata": {},
     "source": [
      "Refinements"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "> Due to Ruby\u2019s open classes you can redefine or add functionality to existing classes. This is called a **monkey patch**. Unfortunately the scope of such changes is global. All users of the monkey-patched class see the same changes. "
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "> Refinements are designed to reduce the impact of monkey patching on other users of the monkey-patched class. Refinements provide a way to extend a class locally."
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "```ruby\n",
      "module TimeExtensions\n",
      "  refine Fixnum do\n",
      "    def minutes; self * 60; end\n",
      "  end\n",
      "end\n",
      "\n",
      "class MyApp\n",
      "  using TimeExtensions\n",
      "\n",
      "  def initialize\n",
      "    p 2.minutes\n",
      "  end\n",
      "end\n",
      "\n",
      "MyApp.new    # => 120\n",
      "p 2.minutes  # => NoMethodError\n",
      "```"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "module JSONGenerator\n",
      "  refine String do\n",
      "    def to_json; inspect end\n",
      "  end\n",
      "  \n",
      "  refine Fixnum do\n",
      "    def to_json; to_s end\n",
      "  end\n",
      "  \n",
      "  refine Array do\n",
      "    def to_json\n",
      "      # Refinements can see one another, so we can use String#to_json and\n",
      "      # Fixnum#to_json as part of the definition of Array#to_json.\n",
      "      \"[\" + map { |x| x.to_json }.join(',') + \"]\"\n",
      "    end\n",
      "  end\n",
      "end"
     ],
     "language": "ruby",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 15,
       "text": [
        "#<refinement:Array@JSONGenerator>"
       ]
      }
     ],
     "prompt_number": 15
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "using JSONGenerator\n",
      "['lorem', 'ipsum', 3].to_json"
     ],
     "language": "ruby",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 14,
       "text": [
        "\"[\\\"lorem\\\",\\\"ipsum\\\",3]\""
       ]
      }
     ],
     "prompt_number": 14
    },
    {
     "cell_type": "heading",
     "level": 3,
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "Subclasses & Reopening"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "```ruby\n",
      "class ApplicationController\n",
      "  using JSONGenerator\n",
      "end\n",
      "\n",
      "# Somewhere else:\n",
      "class ApplicationController\n",
      "  p 123.to_json  # Still works\n",
      "end\n",
      "\n",
      "class UsersController < ApplicationController\n",
      "  p 123.to_json  # Still works\n",
      "end\n",
      "```"
     ]
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "DCI: Data Context Interaction"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "```ruby\n",
      "module Runner\n",
      "  refine User do\n",
      "    def run\n",
      "      puts \"I'm running!\"\n",
      "    end\n",
      "  end\n",
      "end\n",
      "\n",
      "class UserRunsContext\n",
      "  using Runner\n",
      "\n",
      "  def self.call\n",
      "    User.new.run    \n",
      "  end\n",
      "end\n",
      "```"
     ]
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "Still not ready :("
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "module TimeExtensions\n",
      "  refine Fixnum do\n",
      "    def minutes; self * 60; end\n",
      "  end\n",
      "end"
     ],
     "language": "ruby",
     "metadata": {
      "slideshow": {
       "slide_type": "fragment"
      }
     },
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stderr",
       "text": [
        "<main>:1: warning: Refinements are experimental, and the behavior may change in future versions of Ruby!\n"
       ]
      },
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 1,
       "text": [
        "#<refinement:Fixnum@TimeExtensions>"
       ]
      }
     ],
     "prompt_number": 1
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "class Hour\n",
      "  using TimeExtensions\n",
      "  def seconds\n",
      "    60.minutes\n",
      "  end\n",
      "end\n",
      "Hour.new.seconds"
     ],
     "language": "ruby",
     "metadata": {
      "slideshow": {
       "slide_type": "fragment"
      }
     },
     "outputs": [
      {
       "ename": "NoMethodError",
       "evalue": "undefined method `using' for Hour:Class",
       "output_type": "pyerr",
       "traceback": [
        "\u001b[31mNoMethodError\u001b[0m: undefined method `using' for Hour:Class",
        "\u001b[37m<main>:1:in `<class:Hour>'\u001b[0m",
        "\u001b[37m<main>:6:in `<main>'\u001b[0m",
        "\u001b[37m/home/j/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/iruby-0.1.7/lib/iruby/backend.rb:8:in `eval'\u001b[0m",
        "\u001b[37m/home/j/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/iruby-0.1.7/lib/iruby/backend.rb:8:in `eval'\u001b[0m",
        "\u001b[37m/home/j/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/iruby-0.1.7/lib/iruby/kernel.rb:105:in `execute_request'\u001b[0m",
        "\u001b[37m/home/j/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/iruby-0.1.7/lib/iruby/kernel.rb:57:in `run'\u001b[0m",
        "\u001b[37m/home/j/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/iruby-0.1.7/lib/iruby/command.rb:28:in `run_kernel'\u001b[0m",
        "\u001b[37m/home/j/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/iruby-0.1.7/lib/iruby/command.rb:15:in `run'\u001b[0m",
        "\u001b[37m/home/j/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/iruby-0.1.7/bin/iruby:6:in `<top (required)>'\u001b[0m",
        "\u001b[37m/home/j/.rbenv/versions/2.0.0-p247/bin/iruby:23:in `load'\u001b[0m",
        "\u001b[37m/home/j/.rbenv/versions/2.0.0-p247/bin/iruby:23:in `<main>'\u001b[0m"
       ]
      }
     ],
     "prompt_number": 3
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "eval <<-EOF\n",
      "  using TimeExtensions\n",
      "  \n",
      "  class Hour\n",
      "    def seconds\n",
      "      60.minutes\n",
      "    end\n",
      "  end\n",
      "  puts Hour.new.seconds\n",
      "EOF"
     ],
     "language": "ruby",
     "metadata": {
      "slideshow": {
       "slide_type": "fragment"
      }
     },
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "3600\n"
       ]
      }
     ],
     "prompt_number": 2
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "http://bugs.ruby-lang.org/projects/ruby-200/repository/entry/test/ruby/test_refinement.rb"
     ],
     "language": "ruby",
     "metadata": {
      "slideshow": {
       "slide_type": "skip"
      }
     },
     "outputs": []
    },
    {
     "cell_type": "markdown",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "## Resources\n",
      "\n",
      "* http://timelessrepo.com/refinements-in-ruby\n",
      "* http://www.ruby-doc.org/core-2.0.0/doc/syntax/refinements_rdoc.html\n",
      "* http://mikepackdev.com/blog_posts/35-dci-with-ruby-refinements"
     ]
    }
   ],
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