[164] | 1 | == Welcome to Rails
|
---|
| 2 |
|
---|
| 3 | Rails is a web-application framework that includes everything needed to create
|
---|
| 4 | database-backed web applications according to the Model-View-Control pattern.
|
---|
| 5 |
|
---|
| 6 | This pattern splits the view (also called the presentation) into "dumb" templates
|
---|
| 7 | that are primarily responsible for inserting pre-built data in between HTML tags.
|
---|
| 8 | The model contains the "smart" domain objects (such as Account, Product, Person,
|
---|
| 9 | Post) that holds all the business logic and knows how to persist themselves to
|
---|
| 10 | a database. The controller handles the incoming requests (such as Save New Account,
|
---|
| 11 | Update Product, Show Post) by manipulating the model and directing data to the view.
|
---|
| 12 |
|
---|
| 13 | In Rails, the model is handled by what's called an object-relational mapping
|
---|
| 14 | layer entitled Active Record. This layer allows you to present the data from
|
---|
| 15 | database rows as objects and embellish these data objects with business logic
|
---|
| 16 | methods. You can read more about Active Record in
|
---|
| 17 | link:files/vendor/rails/activerecord/README.html.
|
---|
| 18 |
|
---|
| 19 | The controller and view are handled by the Action Pack, which handles both
|
---|
| 20 | layers by its two parts: Action View and Action Controller. These two layers
|
---|
| 21 | are bundled in a single package due to their heavy interdependence. This is
|
---|
| 22 | unlike the relationship between the Active Record and Action Pack that is much
|
---|
| 23 | more separate. Each of these packages can be used independently outside of
|
---|
| 24 | Rails. You can read more about Action Pack in
|
---|
| 25 | link:files/vendor/rails/actionpack/README.html.
|
---|
| 26 |
|
---|
| 27 |
|
---|
| 28 | == Getting Started
|
---|
| 29 |
|
---|
| 30 | 1. At the command prompt, start a new Rails application using the <tt>rails</tt> command
|
---|
| 31 | and your application name. Ex: rails myapp
|
---|
| 32 | 2. Change directory into myapp and start the web server: <tt>script/server</tt> (run with --help for options)
|
---|
| 33 | 3. Go to http://localhost:3000/ and get "Welcome aboard: You're riding the Rails!"
|
---|
| 34 | 4. Follow the guidelines to start developing your application
|
---|
| 35 |
|
---|
| 36 |
|
---|
| 37 | == Web Servers
|
---|
| 38 |
|
---|
| 39 | By default, Rails will try to use Mongrel and lighttpd if they are installed, otherwise
|
---|
| 40 | Rails will use WEBrick, the webserver that ships with Ruby. When you run script/server,
|
---|
| 41 | Rails will check if Mongrel exists, then lighttpd and finally fall back to WEBrick. This ensures
|
---|
| 42 | that you can always get up and running quickly.
|
---|
| 43 |
|
---|
| 44 | Mongrel is a Ruby-based webserver with a C component (which requires compilation) that is
|
---|
| 45 | suitable for development and deployment of Rails applications. If you have Ruby Gems installed,
|
---|
| 46 | getting up and running with mongrel is as easy as: <tt>gem install mongrel</tt>.
|
---|
| 47 | More info at: http://mongrel.rubyforge.org
|
---|
| 48 |
|
---|
| 49 | If Mongrel is not installed, Rails will look for lighttpd. It's considerably faster than
|
---|
| 50 | Mongrel and WEBrick and also suited for production use, but requires additional
|
---|
| 51 | installation and currently only works well on OS X/Unix (Windows users are encouraged
|
---|
| 52 | to start with Mongrel). We recommend version 1.4.11 and higher. You can download it from
|
---|
| 53 | http://www.lighttpd.net.
|
---|
| 54 |
|
---|
| 55 | And finally, if neither Mongrel or lighttpd are installed, Rails will use the built-in Ruby
|
---|
| 56 | web server, WEBrick. WEBrick is a small Ruby web server suitable for development, but not
|
---|
| 57 | for production.
|
---|
| 58 |
|
---|
| 59 | But of course its also possible to run Rails on any platform that supports FCGI.
|
---|
| 60 | Apache, LiteSpeed, IIS are just a few. For more information on FCGI,
|
---|
| 61 | please visit: http://wiki.rubyonrails.com/rails/pages/FastCGI
|
---|
| 62 |
|
---|
| 63 |
|
---|
| 64 | == Apache .htaccess example
|
---|
| 65 |
|
---|
| 66 | # General Apache options
|
---|
| 67 | AddHandler fastcgi-script .fcgi
|
---|
| 68 | AddHandler cgi-script .cgi
|
---|
| 69 | Options +FollowSymLinks +ExecCGI
|
---|
| 70 |
|
---|
| 71 | # If you don't want Rails to look in certain directories,
|
---|
| 72 | # use the following rewrite rules so that Apache won't rewrite certain requests
|
---|
| 73 | #
|
---|
| 74 | # Example:
|
---|
| 75 | # RewriteCond %{REQUEST_URI} ^/notrails.*
|
---|
| 76 | # RewriteRule .* - [L]
|
---|
| 77 |
|
---|
| 78 | # Redirect all requests not available on the filesystem to Rails
|
---|
| 79 | # By default the cgi dispatcher is used which is very slow
|
---|
| 80 | #
|
---|
| 81 | # For better performance replace the dispatcher with the fastcgi one
|
---|
| 82 | #
|
---|
| 83 | # Example:
|
---|
| 84 | # RewriteRule ^(.*)$ dispatch.fcgi [QSA,L]
|
---|
| 85 | RewriteEngine On
|
---|
| 86 |
|
---|
| 87 | # If your Rails application is accessed via an Alias directive,
|
---|
| 88 | # then you MUST also set the RewriteBase in this htaccess file.
|
---|
| 89 | #
|
---|
| 90 | # Example:
|
---|
| 91 | # Alias /myrailsapp /path/to/myrailsapp/public
|
---|
| 92 | # RewriteBase /myrailsapp
|
---|
| 93 |
|
---|
| 94 | RewriteRule ^$ index.html [QSA]
|
---|
| 95 | RewriteRule ^([^.]+)$ $1.html [QSA]
|
---|
| 96 | RewriteCond %{REQUEST_FILENAME} !-f
|
---|
| 97 | RewriteRule ^(.*)$ dispatch.cgi [QSA,L]
|
---|
| 98 |
|
---|
| 99 | # In case Rails experiences terminal errors
|
---|
| 100 | # Instead of displaying this message you can supply a file here which will be rendered instead
|
---|
| 101 | #
|
---|
| 102 | # Example:
|
---|
| 103 | # ErrorDocument 500 /500.html
|
---|
| 104 |
|
---|
| 105 | ErrorDocument 500 "<h2>Application error</h2>Rails application failed to start properly"
|
---|
| 106 |
|
---|
| 107 |
|
---|
| 108 | == Debugging Rails
|
---|
| 109 |
|
---|
| 110 | Sometimes your application goes wrong. Fortunately there are a lot of tools that
|
---|
| 111 | will help you debug it and get it back on the rails.
|
---|
| 112 |
|
---|
| 113 | First area to check is the application log files. Have "tail -f" commands running
|
---|
| 114 | on the server.log and development.log. Rails will automatically display debugging
|
---|
| 115 | and runtime information to these files. Debugging info will also be shown in the
|
---|
| 116 | browser on requests from 127.0.0.1.
|
---|
| 117 |
|
---|
| 118 | You can also log your own messages directly into the log file from your code using
|
---|
| 119 | the Ruby logger class from inside your controllers. Example:
|
---|
| 120 |
|
---|
| 121 | class WeblogController < ActionController::Base
|
---|
| 122 | def destroy
|
---|
| 123 | @weblog = Weblog.find(params[:id])
|
---|
| 124 | @weblog.destroy
|
---|
| 125 | logger.info("#{Time.now} Destroyed Weblog ID ##{@weblog.id}!")
|
---|
| 126 | end
|
---|
| 127 | end
|
---|
| 128 |
|
---|
| 129 | The result will be a message in your log file along the lines of:
|
---|
| 130 |
|
---|
| 131 | Mon Oct 08 14:22:29 +1000 2007 Destroyed Weblog ID #1
|
---|
| 132 |
|
---|
| 133 | More information on how to use the logger is at http://www.ruby-doc.org/core/
|
---|
| 134 |
|
---|
| 135 | Also, Ruby documentation can be found at http://www.ruby-lang.org/ including:
|
---|
| 136 |
|
---|
| 137 | * The Learning Ruby (Pickaxe) Book: http://www.ruby-doc.org/docs/ProgrammingRuby/
|
---|
| 138 | * Learn to Program: http://pine.fm/LearnToProgram/ (a beginners guide)
|
---|
| 139 |
|
---|
| 140 | These two online (and free) books will bring you up to speed on the Ruby language
|
---|
| 141 | and also on programming in general.
|
---|
| 142 |
|
---|
| 143 |
|
---|
| 144 | == Debugger
|
---|
| 145 |
|
---|
| 146 | Debugger support is available through the debugger command when you start your Mongrel or
|
---|
| 147 | Webrick server with --debugger. This means that you can break out of execution at any point
|
---|
| 148 | in the code, investigate and change the model, AND then resume execution!
|
---|
| 149 | You need to install ruby-debug to run the server in debugging mode. With gems, use 'gem install ruby-debug'
|
---|
| 150 | Example:
|
---|
| 151 |
|
---|
| 152 | class WeblogController < ActionController::Base
|
---|
| 153 | def index
|
---|
| 154 | @posts = Post.find(:all)
|
---|
| 155 | debugger
|
---|
| 156 | end
|
---|
| 157 | end
|
---|
| 158 |
|
---|
| 159 | So the controller will accept the action, run the first line, then present you
|
---|
| 160 | with a IRB prompt in the server window. Here you can do things like:
|
---|
| 161 |
|
---|
| 162 | >> @posts.inspect
|
---|
| 163 | => "[#<Post:0x14a6be8 @attributes={\"title\"=>nil, \"body\"=>nil, \"id\"=>\"1\"}>,
|
---|
| 164 | #<Post:0x14a6620 @attributes={\"title\"=>\"Rails you know!\", \"body\"=>\"Only ten..\", \"id\"=>\"2\"}>]"
|
---|
| 165 | >> @posts.first.title = "hello from a debugger"
|
---|
| 166 | => "hello from a debugger"
|
---|
| 167 |
|
---|
| 168 | ...and even better is that you can examine how your runtime objects actually work:
|
---|
| 169 |
|
---|
| 170 | >> f = @posts.first
|
---|
| 171 | => #<Post:0x13630c4 @attributes={"title"=>nil, "body"=>nil, "id"=>"1"}>
|
---|
| 172 | >> f.
|
---|
| 173 | Display all 152 possibilities? (y or n)
|
---|
| 174 |
|
---|
| 175 | Finally, when you're ready to resume execution, you enter "cont"
|
---|
| 176 |
|
---|
| 177 |
|
---|
| 178 | == Console
|
---|
| 179 |
|
---|
| 180 | You can interact with the domain model by starting the console through <tt>script/console</tt>.
|
---|
| 181 | Here you'll have all parts of the application configured, just like it is when the
|
---|
| 182 | application is running. You can inspect domain models, change values, and save to the
|
---|
| 183 | database. Starting the script without arguments will launch it in the development environment.
|
---|
| 184 | Passing an argument will specify a different environment, like <tt>script/console production</tt>.
|
---|
| 185 |
|
---|
| 186 | To reload your controllers and models after launching the console run <tt>reload!</tt>
|
---|
| 187 |
|
---|
| 188 | == dbconsole
|
---|
| 189 |
|
---|
| 190 | You can go to the command line of your database directly through <tt>script/dbconsole</tt>.
|
---|
| 191 | You would be connected to the database with the credentials defined in database.yml.
|
---|
| 192 | Starting the script without arguments will connect you to the development database. Passing an
|
---|
| 193 | argument will connect you to a different database, like <tt>script/dbconsole production</tt>.
|
---|
| 194 | Currently works for mysql, postgresql and sqlite.
|
---|
| 195 |
|
---|
| 196 | == Description of Contents
|
---|
| 197 |
|
---|
| 198 | app
|
---|
| 199 | Holds all the code that's specific to this particular application.
|
---|
| 200 |
|
---|
| 201 | app/controllers
|
---|
| 202 | Holds controllers that should be named like weblogs_controller.rb for
|
---|
| 203 | automated URL mapping. All controllers should descend from ApplicationController
|
---|
| 204 | which itself descends from ActionController::Base.
|
---|
| 205 |
|
---|
| 206 | app/models
|
---|
| 207 | Holds models that should be named like post.rb.
|
---|
| 208 | Most models will descend from ActiveRecord::Base.
|
---|
| 209 |
|
---|
| 210 | app/views
|
---|
| 211 | Holds the template files for the view that should be named like
|
---|
| 212 | weblogs/index.html.erb for the WeblogsController#index action. All views use eRuby
|
---|
| 213 | syntax.
|
---|
| 214 |
|
---|
| 215 | app/views/layouts
|
---|
| 216 | Holds the template files for layouts to be used with views. This models the common
|
---|
| 217 | header/footer method of wrapping views. In your views, define a layout using the
|
---|
| 218 | <tt>layout :default</tt> and create a file named default.html.erb. Inside default.html.erb,
|
---|
| 219 | call <% yield %> to render the view using this layout.
|
---|
| 220 |
|
---|
| 221 | app/helpers
|
---|
| 222 | Holds view helpers that should be named like weblogs_helper.rb. These are generated
|
---|
| 223 | for you automatically when using script/generate for controllers. Helpers can be used to
|
---|
| 224 | wrap functionality for your views into methods.
|
---|
| 225 |
|
---|
| 226 | config
|
---|
| 227 | Configuration files for the Rails environment, the routing map, the database, and other dependencies.
|
---|
| 228 |
|
---|
| 229 | db
|
---|
| 230 | Contains the database schema in schema.rb. db/migrate contains all
|
---|
| 231 | the sequence of Migrations for your schema.
|
---|
| 232 |
|
---|
| 233 | doc
|
---|
| 234 | This directory is where your application documentation will be stored when generated
|
---|
| 235 | using <tt>rake doc:app</tt>
|
---|
| 236 |
|
---|
| 237 | lib
|
---|
| 238 | Application specific libraries. Basically, any kind of custom code that doesn't
|
---|
| 239 | belong under controllers, models, or helpers. This directory is in the load path.
|
---|
| 240 |
|
---|
| 241 | public
|
---|
| 242 | The directory available for the web server. Contains subdirectories for images, stylesheets,
|
---|
| 243 | and javascripts. Also contains the dispatchers and the default HTML files. This should be
|
---|
| 244 | set as the DOCUMENT_ROOT of your web server.
|
---|
| 245 |
|
---|
| 246 | script
|
---|
| 247 | Helper scripts for automation and generation.
|
---|
| 248 |
|
---|
| 249 | test
|
---|
| 250 | Unit and functional tests along with fixtures. When using the script/generate scripts, template
|
---|
| 251 | test files will be generated for you and placed in this directory.
|
---|
| 252 |
|
---|
| 253 | vendor
|
---|
| 254 | External libraries that the application depends on. Also includes the plugins subdirectory.
|
---|
| 255 | If the app has frozen rails, those gems also go here, under vendor/rails/.
|
---|
| 256 | This directory is in the load path.
|
---|