{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 4-1-3 インスタンス変数へのアクセス"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "nil\n",
      "30\n",
      "30\n"
     ]
    },
    {
     "data": {
      "text/plain": [
       "30"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "class Ruler\n",
    "  attr_accessor :length\n",
    "end\n",
    "\n",
    "class Ruler2\n",
    "  def length=(length)\n",
    "    @length = length\n",
    "  end\n",
    "  \n",
    "  def length\n",
    "    @length\n",
    "  end\n",
    "end\n",
    "  \n",
    "ruler = Ruler.new\n",
    "p ruler.length\n",
    "p ruler.length = 30\n",
    "p ruler.length"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "nil\n",
      "30\n",
      "30\n"
     ]
    },
    {
     "data": {
      "text/plain": [
       "30"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "ruler2 = Ruler2.new\n",
    "p ruler2.length\n",
    "p ruler2.length = 30\n",
    "p ruler2.length"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {
    "collapsed": false,
    "scrolled": true
   },
   "outputs": [
    {
     "ename": "NameError",
     "evalue": "invalid attribute name `foo?'",
     "output_type": "error",
     "traceback": [
      "\u001b[31mNameError\u001b[0m: invalid attribute name `foo?'",
      "\u001b[37m(pry):56:in `attr_accessor'\u001b[0m",
      "\u001b[37m(pry):56:in `<class:Hoge>'\u001b[0m",
      "\u001b[37m(pry):55:in `<main>'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/pry-0.10.1/lib/pry/pry_instance.rb:355:in `eval'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/pry-0.10.1/lib/pry/pry_instance.rb:355:in `evaluate_ruby'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/pry-0.10.1/lib/pry/pry_instance.rb:323:in `handle_line'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/pry-0.10.1/lib/pry/pry_instance.rb:243:in `block (2 levels) in eval'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/pry-0.10.1/lib/pry/pry_instance.rb:242:in `catch'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/pry-0.10.1/lib/pry/pry_instance.rb:242:in `block in eval'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/pry-0.10.1/lib/pry/pry_instance.rb:241:in `catch'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/pry-0.10.1/lib/pry/pry_instance.rb:241:in `eval'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/iruby-0.2.7/lib/iruby/backend.rb:65:in `eval'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/iruby-0.2.7/lib/iruby/backend.rb:12:in `eval'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/iruby-0.2.7/lib/iruby/kernel.rb:87:in `execute_request'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/iruby-0.2.7/lib/iruby/kernel.rb:47:in `dispatch'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/iruby-0.2.7/lib/iruby/kernel.rb:37:in `run'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/iruby-0.2.7/lib/iruby/command.rb:70:in `run_kernel'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/iruby-0.2.7/lib/iruby/command.rb:34:in `run'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/iruby-0.2.7/bin/iruby:5:in `<top (required)>'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/bin/iruby:23:in `load'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/bin/iruby:23:in `<main>'\u001b[0m"
     ]
    }
   ],
   "source": [
    "class Hoge\n",
    "  attr_accessor :foo?\n",
    "end"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "class Rectangle\n",
    "  attr_accessor :width, :heght\n",
    "end\n",
    "\n",
    "# 上と同じ\n",
    "class Rectangle2\n",
    "  attr_reader  :width, :heght\n",
    "  attr_writer  :width, :heght\n",
    "end"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 4-1-4 クラスメソッド"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[#<Ruler:0x007fdf5c938c88>, #<Ruler:0x007fdf5c938c38>]"
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "class Ruler\n",
    "  attr_accessor :length\n",
    "  \n",
    "  def self.pair\n",
    "    [self.new, self.new]\n",
    "  end\n",
    "end\n",
    "\n",
    "Ruler.pair"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[#<Ruler:0x007fdf5d819108>, #<Ruler:0x007fdf5d8190b8>]"
      ]
     },
     "execution_count": 10,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "class Ruler\n",
    "  attr_accessor :length\n",
    "  \n",
    "  def double_length\n",
    "    length * 2\n",
    "  end\n",
    "  private :double_length\n",
    "  \n",
    "  class << self\n",
    "    def pair\n",
    "      [new, new]\n",
    "    end\n",
    "    \n",
    "    def trie\n",
    "      [new, new, new]\n",
    "    end\n",
    "  end\n",
    "end\n",
    "\n",
    "Ruler.pair"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "ename": "NoMethodError",
     "evalue": "private method `double_length' called for #<Ruler:0x007fdf5d8fd9c0>",
     "output_type": "error",
     "traceback": [
      "\u001b[31mNoMethodError\u001b[0m: private method `double_length' called for #<Ruler:0x007fdf5d8fd9c0>",
      "\u001b[37m(pry):127:in `<main>'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/pry-0.10.1/lib/pry/pry_instance.rb:355:in `eval'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/pry-0.10.1/lib/pry/pry_instance.rb:355:in `evaluate_ruby'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/pry-0.10.1/lib/pry/pry_instance.rb:323:in `handle_line'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/pry-0.10.1/lib/pry/pry_instance.rb:243:in `block (2 levels) in eval'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/pry-0.10.1/lib/pry/pry_instance.rb:242:in `catch'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/pry-0.10.1/lib/pry/pry_instance.rb:242:in `block in eval'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/pry-0.10.1/lib/pry/pry_instance.rb:241:in `catch'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/pry-0.10.1/lib/pry/pry_instance.rb:241:in `eval'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/iruby-0.2.7/lib/iruby/backend.rb:65:in `eval'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/iruby-0.2.7/lib/iruby/backend.rb:12:in `eval'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/iruby-0.2.7/lib/iruby/kernel.rb:87:in `execute_request'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/iruby-0.2.7/lib/iruby/kernel.rb:47:in `dispatch'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/iruby-0.2.7/lib/iruby/kernel.rb:37:in `run'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/iruby-0.2.7/lib/iruby/command.rb:70:in `run_kernel'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/iruby-0.2.7/lib/iruby/command.rb:34:in `run'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/iruby-0.2.7/bin/iruby:5:in `<top (required)>'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/bin/iruby:23:in `load'\u001b[0m",
      "\u001b[37m/Users/mic/.rbenv/versions/2.2.2/bin/iruby:23:in `<main>'\u001b[0m"
     ]
    }
   ],
   "source": [
    "ruler = Ruler.new\n",
    "ruler.double_length"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": []
  }
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