[12] | 1 | == Welcome to Rails
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| 2 |
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| 3 | Rails is a web-application and persistence framework that includes everything
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| 4 | needed to create database-backed web-applications according to the
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| 5 | Model-View-Control pattern of separation. This pattern splits the view (also
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| 6 | called the presentation) into "dumb" templates that are primarily responsible
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| 7 | for inserting pre-built data in between HTML tags. The model contains the
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| 8 | "smart" domain objects (such as Account, Product, Person, Post) that holds all
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| 9 | the business logic and knows how to persist themselves to a database. The
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| 10 | controller handles the incoming requests (such as Save New Account, Update
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| 11 | Product, Show Post) by manipulating the model and directing data to the view.
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| 12 |
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| 13 | In Rails, the model is handled by what's called an object-relational mapping
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| 14 | layer entitled Active Record. This layer allows you to present the data from
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| 15 | database rows as objects and embellish these data objects with business logic
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| 16 | methods. You can read more about Active Record in
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| 17 | link:files/vendor/rails/activerecord/README.html.
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| 18 |
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| 19 | The controller and view are handled by the Action Pack, which handles both
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| 20 | layers by its two parts: Action View and Action Controller. These two layers
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| 21 | are bundled in a single package due to their heavy interdependence. This is
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| 22 | unlike the relationship between the Active Record and Action Pack that is much
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| 23 | more separate. Each of these packages can be used independently outside of
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| 24 | Rails. You can read more about Action Pack in
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| 25 | link:files/vendor/rails/actionpack/README.html.
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| 26 |
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| 27 |
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| 28 | == Getting Started
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| 29 |
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| 30 | 1. At the command prompt, start a new Rails application using the <tt>rails</tt> command
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| 31 | and your application name. Ex: rails myapp
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| 32 | (If you've downloaded Rails in a complete tgz or zip, this step is already done)
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| 33 | 2. Change directory into myapp and start the web server: <tt>script/server</tt> (run with --help for options)
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| 34 | 3. Go to http://localhost:3000/ and get "Welcome aboard: You’re riding the Rails!"
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| 35 | 4. Follow the guidelines to start developing your application
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| 36 |
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| 37 |
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| 38 | == Web Servers
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| 39 |
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| 40 | By default, Rails will try to use Mongrel and lighttpd if they are installed, otherwise
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| 41 | Rails will use WEBrick, the webserver that ships with Ruby. When you run script/server,
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| 42 | Rails will check if Mongrel exists, then lighttpd and finally fall back to WEBrick. This ensures
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| 43 | that you can always get up and running quickly.
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| 44 |
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| 45 | Mongrel is a Ruby-based webserver with a C component (which requires compilation) that is
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| 46 | suitable for development and deployment of Rails applications. If you have Ruby Gems installed,
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| 47 | getting up and running with mongrel is as easy as: <tt>gem install mongrel</tt>.
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| 48 | More info at: http://mongrel.rubyforge.org
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| 49 |
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| 50 | If Mongrel is not installed, Rails will look for lighttpd. It's considerably faster than
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| 51 | Mongrel and WEBrick and also suited for production use, but requires additional
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| 52 | installation and currently only works well on OS X/Unix (Windows users are encouraged
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| 53 | to start with Mongrel). We recommend version 1.4.11 and higher. You can download it from
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| 54 | http://www.lighttpd.net.
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| 55 |
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| 56 | And finally, if neither Mongrel or lighttpd are installed, Rails will use the built-in Ruby
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| 57 | web server, WEBrick. WEBrick is a small Ruby web server suitable for development, but not
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| 58 | for production.
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| 59 |
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| 60 | But of course its also possible to run Rails on any platform that supports FCGI.
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| 61 | Apache, LiteSpeed, IIS are just a few. For more information on FCGI,
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| 62 | please visit: http://wiki.rubyonrails.com/rails/pages/FastCGI
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| 63 |
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| 64 |
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| 65 | == Debugging Rails
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| 66 |
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| 67 | Sometimes your application goes wrong. Fortunately there are a lot of tools that
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| 68 | will help you debug it and get it back on the rails.
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| 69 |
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| 70 | First area to check is the application log files. Have "tail -f" commands running
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| 71 | on the server.log and development.log. Rails will automatically display debugging
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| 72 | and runtime information to these files. Debugging info will also be shown in the
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| 73 | browser on requests from 127.0.0.1.
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| 74 |
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| 75 | You can also log your own messages directly into the log file from your code using
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| 76 | the Ruby logger class from inside your controllers. Example:
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| 77 |
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| 78 | class WeblogController < ActionController::Base
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| 79 | def destroy
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| 80 | @weblog = Weblog.find(params[:id])
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| 81 | @weblog.destroy
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| 82 | logger.info("#{Time.now} Destroyed Weblog ID ##{@weblog.id}!")
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| 83 | end
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| 84 | end
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| 85 |
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| 86 | The result will be a message in your log file along the lines of:
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| 87 |
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| 88 | Mon Oct 08 14:22:29 +1000 2007 Destroyed Weblog ID #1
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| 89 |
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| 90 | More information on how to use the logger is at http://www.ruby-doc.org/core/
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| 91 |
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| 92 | Also, Ruby documentation can be found at http://www.ruby-lang.org/ including:
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| 93 |
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| 94 | * The Learning Ruby (Pickaxe) Book: http://www.ruby-doc.org/docs/ProgrammingRuby/
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| 95 | * Learn to Program: http://pine.fm/LearnToProgram/ (a beginners guide)
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| 96 |
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| 97 | These two online (and free) books will bring you up to speed on the Ruby language
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| 98 | and also on programming in general.
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| 99 |
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| 100 |
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| 101 | == Debugger
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| 102 |
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| 103 | Debugger support is available through the debugger command when you start your Mongrel or
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| 104 | Webrick server with --debugger. This means that you can break out of execution at any point
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| 105 | in the code, investigate and change the model, AND then resume execution! Example:
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| 106 |
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| 107 | class WeblogController < ActionController::Base
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| 108 | def index
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| 109 | @posts = Post.find(:all)
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| 110 | debugger
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| 111 | end
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| 112 | end
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| 113 |
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| 114 | So the controller will accept the action, run the first line, then present you
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| 115 | with a IRB prompt in the server window. Here you can do things like:
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| 116 |
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| 117 | >> @posts.inspect
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| 118 | => "[#<Post:0x14a6be8 @attributes={\"title\"=>nil, \"body\"=>nil, \"id\"=>\"1\"}>,
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| 119 | #<Post:0x14a6620 @attributes={\"title\"=>\"Rails you know!\", \"body\"=>\"Only ten..\", \"id\"=>\"2\"}>]"
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| 120 | >> @posts.first.title = "hello from a debugger"
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| 121 | => "hello from a debugger"
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| 122 |
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| 123 | ...and even better is that you can examine how your runtime objects actually work:
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| 124 |
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| 125 | >> f = @posts.first
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| 126 | => #<Post:0x13630c4 @attributes={"title"=>nil, "body"=>nil, "id"=>"1"}>
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| 127 | >> f.
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| 128 | Display all 152 possibilities? (y or n)
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| 129 |
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| 130 | Finally, when you're ready to resume execution, you enter "cont"
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| 131 |
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| 132 |
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| 133 | == Console
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| 134 |
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| 135 | You can interact with the domain model by starting the console through <tt>script/console</tt>.
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| 136 | Here you'll have all parts of the application configured, just like it is when the
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| 137 | application is running. You can inspect domain models, change values, and save to the
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| 138 | database. Starting the script without arguments will launch it in the development environment.
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| 139 | Passing an argument will specify a different environment, like <tt>script/console production</tt>.
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| 140 |
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| 141 | To reload your controllers and models after launching the console run <tt>reload!</tt>
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| 142 |
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| 143 |
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| 144 | == Description of Contents
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| 145 |
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| 146 | app
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| 147 | Holds all the code that's specific to this particular application.
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| 148 |
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| 149 | app/controllers
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| 150 | Holds controllers that should be named like weblogs_controller.rb for
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| 151 | automated URL mapping. All controllers should descend from ApplicationController
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| 152 | which itself descends from ActionController::Base.
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| 153 |
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| 154 | app/models
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| 155 | Holds models that should be named like post.rb.
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| 156 | Most models will descend from ActiveRecord::Base.
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| 157 |
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| 158 | app/views
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| 159 | Holds the template files for the view that should be named like
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| 160 | weblogs/index.erb for the WeblogsController#index action. All views use eRuby
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| 161 | syntax.
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| 162 |
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| 163 | app/views/layouts
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| 164 | Holds the template files for layouts to be used with views. This models the common
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| 165 | header/footer method of wrapping views. In your views, define a layout using the
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| 166 | <tt>layout :default</tt> and create a file named default.erb. Inside default.erb,
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| 167 | call <% yield %> to render the view using this layout.
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| 168 |
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| 169 | app/helpers
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| 170 | Holds view helpers that should be named like weblogs_helper.rb. These are generated
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| 171 | for you automatically when using script/generate for controllers. Helpers can be used to
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| 172 | wrap functionality for your views into methods.
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| 173 |
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| 174 | config
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| 175 | Configuration files for the Rails environment, the routing map, the database, and other dependencies.
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| 176 |
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| 177 | db
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| 178 | Contains the database schema in schema.rb. db/migrate contains all
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| 179 | the sequence of Migrations for your schema.
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| 180 |
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| 181 | doc
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| 182 | This directory is where your application documentation will be stored when generated
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| 183 | using <tt>rake doc:app</tt>
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| 184 |
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| 185 | lib
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| 186 | Application specific libraries. Basically, any kind of custom code that doesn't
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| 187 | belong under controllers, models, or helpers. This directory is in the load path.
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| 188 |
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| 189 | public
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| 190 | The directory available for the web server. Contains subdirectories for images, stylesheets,
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| 191 | and javascripts. Also contains the dispatchers and the default HTML files. This should be
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| 192 | set as the DOCUMENT_ROOT of your web server.
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| 193 |
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| 194 | script
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| 195 | Helper scripts for automation and generation.
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| 196 |
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| 197 | test
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| 198 | Unit and functional tests along with fixtures. When using the script/generate scripts, template
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| 199 | test files will be generated for you and placed in this directory.
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| 200 |
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| 201 | vendor
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| 202 | External libraries that the application depends on. Also includes the plugins subdirectory.
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| 203 | This directory is in the load path.
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