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1 == Welcome to Rails
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2
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3 Rails is a web-application framework that includes everything needed to create
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4 database-backed web applications according to the Model-View-Control pattern.
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5
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6 This pattern splits the view (also called the presentation) into "dumb"
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7 templates that are primarily responsible for inserting pre-built data in between
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8 HTML tags. The model contains the "smart" domain objects (such as Account,
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9 Product, Person, Post) that holds all the business logic and knows how to
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10 persist themselves to a database. The controller handles the incoming requests
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11 (such as Save New Account, Update Product, Show Post) by manipulating the model
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12 and directing data to the view.
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13
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14 In Rails, the model is handled by what's called an object-relational mapping
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15 layer entitled Active Record. This layer allows you to present the data from
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16 database rows as objects and embellish these data objects with business logic
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17 methods. You can read more about Active Record in
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18 link:files/vendor/rails/activerecord/README.html.
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19
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20 The controller and view are handled by the Action Pack, which handles both
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21 layers by its two parts: Action View and Action Controller. These two layers
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22 are bundled in a single package due to their heavy interdependence. This is
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23 unlike the relationship between the Active Record and Action Pack that is much
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24 more separate. Each of these packages can be used independently outside of
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25 Rails. You can read more about Action Pack in
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26 link:files/vendor/rails/actionpack/README.html.
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27
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28
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29 == Getting Started
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30
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31 1. At the command prompt, create a new Rails application:
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32 <tt>rails new myapp</tt> (where <tt>myapp</tt> is the application name)
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33
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34 2. Change directory to <tt>myapp</tt> and start the web server:
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35 <tt>cd myapp; rails server</tt> (run with --help for options)
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36
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37 3. Go to http://localhost:3000/ and you'll see:
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38 "Welcome aboard: You're riding Ruby on Rails!"
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39
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40 4. Follow the guidelines to start developing your application. You can find
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41 the following resources handy:
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42
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43 * The Getting Started Guide: http://guides.rubyonrails.org/getting_started.html
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44 * Ruby on Rails Tutorial Book: http://www.railstutorial.org/
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45
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46
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47 == Debugging Rails
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48
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49 Sometimes your application goes wrong. Fortunately there are a lot of tools that
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50 will help you debug it and get it back on the rails.
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51
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52 First area to check is the application log files. Have "tail -f" commands
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53 running on the server.log and development.log. Rails will automatically display
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54 debugging and runtime information to these files. Debugging info will also be
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55 shown in the browser on requests from 127.0.0.1.
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56
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57 You can also log your own messages directly into the log file from your code
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58 using the Ruby logger class from inside your controllers. Example:
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59
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60 class WeblogController < ActionController::Base
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61 def destroy
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62 @weblog = Weblog.find(params[:id])
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63 @weblog.destroy
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64 logger.info("#{Time.now} Destroyed Weblog ID ##{@weblog.id}!")
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65 end
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66 end
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67
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68 The result will be a message in your log file along the lines of:
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69
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70 Mon Oct 08 14:22:29 +1000 2007 Destroyed Weblog ID #1!
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71
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72 More information on how to use the logger is at http://www.ruby-doc.org/core/
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73
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74 Also, Ruby documentation can be found at http://www.ruby-lang.org/. There are
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75 several books available online as well:
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76
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77 * Programming Ruby: http://www.ruby-doc.org/docs/ProgrammingRuby/ (Pickaxe)
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78 * Learn to Program: http://pine.fm/LearnToProgram/ (a beginners guide)
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79
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80 These two books will bring you up to speed on the Ruby language and also on
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81 programming in general.
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82
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83
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84 == Debugger
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85
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86 Debugger support is available through the debugger command when you start your
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87 Mongrel or WEBrick server with --debugger. This means that you can break out of
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88 execution at any point in the code, investigate and change the model, and then,
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89 resume execution! You need to install ruby-debug to run the server in debugging
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90 mode. With gems, use <tt>sudo gem install ruby-debug</tt>. Example:
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91
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92 class WeblogController < ActionController::Base
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93 def index
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94 @posts = Post.all
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95 debugger
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96 end
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97 end
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98
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99 So the controller will accept the action, run the first line, then present you
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100 with a IRB prompt in the server window. Here you can do things like:
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101
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102 >> @posts.inspect
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103 => "[#<Post:0x14a6be8
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104 @attributes={"title"=>nil, "body"=>nil, "id"=>"1"}>,
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105 #<Post:0x14a6620
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106 @attributes={"title"=>"Rails", "body"=>"Only ten..", "id"=>"2"}>]"
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107 >> @posts.first.title = "hello from a debugger"
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108 => "hello from a debugger"
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109
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110 ...and even better, you can examine how your runtime objects actually work:
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111
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112 >> f = @posts.first
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113 => #<Post:0x13630c4 @attributes={"title"=>nil, "body"=>nil, "id"=>"1"}>
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114 >> f.
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115 Display all 152 possibilities? (y or n)
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116
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117 Finally, when you're ready to resume execution, you can enter "cont".
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118
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119
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120 == Console
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121
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122 The console is a Ruby shell, which allows you to interact with your
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123 application's domain model. Here you'll have all parts of the application
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124 configured, just like it is when the application is running. You can inspect
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125 domain models, change values, and save to the database. Starting the script
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126 without arguments will launch it in the development environment.
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127
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128 To start the console, run <tt>rails console</tt> from the application
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129 directory.
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130
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131 Options:
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132
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133 * Passing the <tt>-s, --sandbox</tt> argument will rollback any modifications
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134 made to the database.
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135 * Passing an environment name as an argument will load the corresponding
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136 environment. Example: <tt>rails console production</tt>.
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137
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138 To reload your controllers and models after launching the console run
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139 <tt>reload!</tt>
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140
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141 More information about irb can be found at:
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142 link:http://www.rubycentral.org/pickaxe/irb.html
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143
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144
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145 == dbconsole
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146
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147 You can go to the command line of your database directly through <tt>rails
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148 dbconsole</tt>. You would be connected to the database with the credentials
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149 defined in database.yml. Starting the script without arguments will connect you
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150 to the development database. Passing an argument will connect you to a different
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151 database, like <tt>rails dbconsole production</tt>. Currently works for MySQL,
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152 PostgreSQL and SQLite 3.
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153
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154 == Description of Contents
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155
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156 The default directory structure of a generated Ruby on Rails application:
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157
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158 |-- app
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159 | |-- assets
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160 | |-- images
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161 | |-- javascripts
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162 | `-- stylesheets
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163 | |-- controllers
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164 | |-- helpers
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165 | |-- mailers
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166 | |-- models
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167 | `-- views
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168 | `-- layouts
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169 |-- config
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170 | |-- environments
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171 | |-- initializers
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172 | `-- locales
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173 |-- db
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174 |-- doc
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175 |-- lib
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176 | `-- tasks
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177 |-- log
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178 |-- public
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179 |-- script
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180 |-- test
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181 | |-- fixtures
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182 | |-- functional
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183 | |-- integration
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184 | |-- performance
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185 | `-- unit
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186 |-- tmp
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187 | |-- cache
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188 | |-- pids
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189 | |-- sessions
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190 | `-- sockets
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191 `-- vendor
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192 |-- assets
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193 `-- stylesheets
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194 `-- plugins
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195
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196 app
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197 Holds all the code that's specific to this particular application.
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198
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199 app/assets
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200 Contains subdirectories for images, stylesheets, and JavaScript files.
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201
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202 app/controllers
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203 Holds controllers that should be named like weblogs_controller.rb for
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204 automated URL mapping. All controllers should descend from
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205 ApplicationController which itself descends from ActionController::Base.
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206
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207 app/models
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208 Holds models that should be named like post.rb. Models descend from
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209 ActiveRecord::Base by default.
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210
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211 app/views
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212 Holds the template files for the view that should be named like
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213 weblogs/index.html.erb for the WeblogsController#index action. All views use
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214 eRuby syntax by default.
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215
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216 app/views/layouts
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217 Holds the template files for layouts to be used with views. This models the
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218 common header/footer method of wrapping views. In your views, define a layout
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219 using the <tt>layout :default</tt> and create a file named default.html.erb.
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220 Inside default.html.erb, call <% yield %> to render the view using this
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221 layout.
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222
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223 app/helpers
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224 Holds view helpers that should be named like weblogs_helper.rb. These are
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225 generated for you automatically when using generators for controllers.
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226 Helpers can be used to wrap functionality for your views into methods.
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227
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228 config
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229 Configuration files for the Rails environment, the routing map, the database,
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230 and other dependencies.
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231
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232 db
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233 Contains the database schema in schema.rb. db/migrate contains all the
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234 sequence of Migrations for your schema.
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235
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236 doc
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237 This directory is where your application documentation will be stored when
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238 generated using <tt>rake doc:app</tt>
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239
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240 lib
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241 Application specific libraries. Basically, any kind of custom code that
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242 doesn't belong under controllers, models, or helpers. This directory is in
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243 the load path.
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244
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245 public
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246 The directory available for the web server. Also contains the dispatchers and the
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247 default HTML files. This should be set as the DOCUMENT_ROOT of your web
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248 server.
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249
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250 script
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251 Helper scripts for automation and generation.
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252
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253 test
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254 Unit and functional tests along with fixtures. When using the rails generate
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255 command, template test files will be generated for you and placed in this
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256 directory.
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257
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258 vendor
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259 External libraries that the application depends on. Also includes the plugins
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260 subdirectory. If the app has frozen rails, those gems also go here, under
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261 vendor/rails/. This directory is in the load path.
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