410 lines
13 KiB
Plaintext
410 lines
13 KiB
Plaintext
= Action Pack -- On rails from request to response
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Action Pack splits the response to a web request into a controller part
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(performing the logic) and a view part (rendering a template). This two-step
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approach is known as an action, which will normally create, read, update, or
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delete (CRUD for short) some sort of model part (often backed by a database)
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before choosing either to render a template or redirecting to another action.
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Action Pack implements these actions as public methods on Action Controllers
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and uses Action Views to implement the template rendering. Action Controllers
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are then responsible for handling all the actions relating to a certain part
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of an application. This grouping usually consists of actions for lists and for
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CRUDs revolving around a single (or a few) model objects. So ContactsController
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would be responsible for listing contacts, creating, deleting, and updating
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contacts. A WeblogController could be responsible for both posts and comments.
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Action View templates are written using embedded Ruby in tags mingled in with
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the HTML. To avoid cluttering the templates with code, a bunch of helper
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classes provide common behavior for forms, dates, and strings. And it's easy
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to add specific helpers to keep the separation as the application evolves.
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Note: Some of the features, such as scaffolding and form building, are tied to
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ActiveRecord[http://activerecord.rubyonrails.org] (an object-relational
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mapping package), but that doesn't mean that Action Pack depends on Active
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Record. Action Pack is an independent package that can be used with any sort
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of backend (Instiki[http://www.instiki.org], which is based on an older version
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of Action Pack, used Madeleine for example). Read more about the role Action
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Pack can play when used together with Active Record on
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http://www.rubyonrails.org.
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A short rundown of the major features:
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* Actions grouped in controller as methods instead of separate command objects
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and can therefore share helper methods
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CustomersController < ActionController::Base
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def show
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@customer = find_customer
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end
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def update
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@customer = find_customer
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@customer.attributes = params[:customer]
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@customer.save ?
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redirect_to(:action => "show") :
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render(:action => "edit")
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end
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private
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def find_customer() Customer.find(params[:id]) end
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end
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{Learn more}[link:classes/ActionController/Base.html]
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* Embedded Ruby for templates (no new "easy" template language)
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<% for post in @posts %>
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Title: <%= post.title %>
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<% end %>
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All post titles: <%= @posts.collect{ |p| p.title }.join ", " %>
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<% unless @person.is_client? %>
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Not for clients to see...
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<% end %>
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{Learn more}[link:classes/ActionView.html]
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* Builder-based templates (great for XML content, like RSS)
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xml.rss("version" => "2.0") do
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xml.channel do
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xml.title(@feed_title)
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xml.link(@url)
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xml.description "Basecamp: Recent items"
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xml.language "en-us"
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xml.ttl "40"
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for item in @recent_items
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xml.item do
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xml.title(item_title(item))
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xml.description(item_description(item))
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xml.pubDate(item_pubDate(item))
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xml.guid(@recent_items.url(item))
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xml.link(@recent_items.url(item))
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end
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end
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end
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end
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{Learn more}[link:classes/ActionView/Base.html]
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* Filters for pre and post processing of the response (as methods, procs, and classes)
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class WeblogController < ActionController::Base
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before_filter :authenticate, :cache, :audit
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after_filter { |c| c.response.body = Gzip::compress(c.response.body) }
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after_filter LocalizeFilter
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def index
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# Before this action is run, the user will be authenticated, the cache
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# will be examined to see if a valid copy of the results already
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# exists, and the action will be logged for auditing.
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# After this action has run, the output will first be localized then
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# compressed to minimize bandwidth usage
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end
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private
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def authenticate
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# Implement the filter with full access to both request and response
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end
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end
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{Learn more}[link:classes/ActionController/Filters/ClassMethods.html]
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* Helpers for forms, dates, action links, and text
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<%= text_field "post", "title", "size" => 30 %>
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<%= html_date_select(Date.today) %>
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<%= link_to "New post", :controller => "post", :action => "new" %>
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<%= truncate(post.title, :length => 25) %>
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{Learn more}[link:classes/ActionView/Helpers.html]
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* Layout sharing for template reuse (think simple version of Struts
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Tiles[http://jakarta.apache.org/struts/userGuide/dev_tiles.html])
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class WeblogController < ActionController::Base
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layout "weblog_layout"
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def hello_world
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end
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end
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Layout file (called weblog_layout):
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<html><body><%= yield %></body></html>
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Template for hello_world action:
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<h1>Hello world</h1>
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Result of running hello_world action:
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<html><body><h1>Hello world</h1></body></html>
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{Learn more}[link:classes/ActionController/Layout/ClassMethods.html]
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* Routing makes pretty urls incredibly easy
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map.connect 'clients/:client_name/:project_name/:controller/:action'
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Accessing /clients/37signals/basecamp/project/dash calls ProjectController#dash with
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{ "client_name" => "37signals", "project_name" => "basecamp" }.
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From that URL you can redirect providing new parameters in a number of ways:
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redirect_to :action => "edit"
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# /clients/37signals/basecamp/project/edit
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redirect_to :client_name => "nextangle", :project_name => "rails"
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# /clients/nextangle/rails/project/dash
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{Learn more}[link:classes/ActionController/Base.html]
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* JavaScript and Ajax integration
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link_to_function "Greeting", "alert('Hello world!')"
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link_to_remote "Delete this post", :update => "posts",
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:url => { :action => "destroy", :id => post.id }
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{Learn more}[link:classes/ActionView/Helpers/JavaScriptHelper.html]
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* Easy testing of both controller and rendered template through ActionController::TestCase
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class LoginControllerTest < ActionController::TestCase
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def test_failing_authenticate
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process :authenticate, :user_name => "nop", :password => ""
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assert flash.has_key?(:alert)
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assert_redirected_to :action => "index"
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end
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end
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{Learn more}[link:classes/ActionController/TestCase.html]
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* Automated benchmarking and integrated logging
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Processing WeblogController#index (for 127.0.0.1 at Fri May 28 00:41:55)
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Parameters: {"action"=>"index", "controller"=>"weblog"}
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Rendering weblog/index (200 OK)
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Completed in 0.029281 (34 reqs/sec)
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If Active Record is used as the model, you'll have the database debugging
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as well:
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Processing PostsController#create (for 127.0.0.1 at Sat Jun 19 14:04:23)
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Params: {"controller"=>"posts", "action"=>"create",
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"post"=>{"title"=>"this is good"} }
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SQL (0.000627) INSERT INTO posts (title) VALUES('this is good')
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Redirected to http://example.com/posts/5
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Completed in 0.221764 (4 reqs/sec) | DB: 0.059920 (27%)
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You specify a logger through a class method, such as:
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ActionController::Base.logger = Logger.new("Application Log")
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ActionController::Base.logger = Log4r::Logger.new("Application Log")
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* Caching at three levels of granularity (page, action, fragment)
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class WeblogController < ActionController::Base
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caches_page :show
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caches_action :account
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def show
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# the output of the method will be cached as
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# ActionController::Base.page_cache_directory + "/weblog/show/n.html"
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# and the web server will pick it up without even hitting Rails
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end
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def account
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# the output of the method will be cached in the fragment store
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# but Rails is hit to retrieve it, so filters are run
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end
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def update
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List.update(params[:list][:id], params[:list])
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expire_page :action => "show", :id => params[:list][:id]
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expire_action :action => "account"
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redirect_to :action => "show", :id => params[:list][:id]
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end
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end
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{Learn more}[link:classes/ActionController/Caching.html]
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* Powerful debugging mechanism for local requests
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All exceptions raised on actions performed on the request of a local user
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will be presented with a tailored debugging screen that includes exception
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message, stack trace, request parameters, session contents, and the
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half-finished response.
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{Learn more}[link:classes/ActionController/Rescue.html]
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* Scaffolding for Active Record model objects
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class AccountController < ActionController::Base
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scaffold :account
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end
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The AccountController now has the full CRUD range of actions and default
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templates: list, show, destroy, new, create, edit, update
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{Learn more}[link:classes/ActionController/Scaffolding/ClassMethods.html]
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* Form building for Active Record model objects
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The post object has a title (varchar), content (text), and
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written_on (date)
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<%= form "post" %>
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...will generate something like (the selects will have more options, of
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course):
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<form action="create" method="POST">
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<p>
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<b>Title:</b><br/>
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<input type="text" name="post[title]" value="<%= @post.title %>" />
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</p>
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<p>
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<b>Content:</b><br/>
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<textarea name="post[content]"><%= @post.title %></textarea>
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</p>
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<p>
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<b>Written on:</b><br/>
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<select name='post[written_on(3i)]'><option>18</option></select>
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<select name='post[written_on(2i)]'><option value='7'>July</option></select>
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<select name='post[written_on(1i)]'><option>2004</option></select>
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</p>
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<input type="submit" value="Create">
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</form>
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This form generates a params[:post] array that can be used directly in a save action:
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class WeblogController < ActionController::Base
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def create
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post = Post.create(params[:post])
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redirect_to :action => "show", :id => post.id
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end
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end
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{Learn more}[link:classes/ActionView/Helpers/ActiveRecordHelper.html]
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* Runs on top of WEBrick, Mongrel, CGI, FCGI, and mod_ruby
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== Simple example (from outside of Rails)
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This example will implement a simple weblog system using inline templates and
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an Active Record model. So let's build that WeblogController with just a few
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methods:
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require 'action_controller'
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require 'post'
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class WeblogController < ActionController::Base
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layout "weblog/layout"
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def index
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@posts = Post.find(:all)
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end
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def show
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@post = Post.find(params[:id])
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end
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def new
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@post = Post.new
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end
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def create
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@post = Post.create(params[:post])
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redirect_to :action => "show", :id => @post.id
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end
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end
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WeblogController::Base.view_paths = [ File.dirname(__FILE__) ]
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WeblogController.process_cgi if $0 == __FILE__
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The last two lines are responsible for telling ActionController where the
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template files are located and actually running the controller on a new
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request from the web-server (like to be Apache).
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And the templates look like this:
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weblog/layout.html.erb:
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<html><body>
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<%= yield %>
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</body></html>
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weblog/index.html.erb:
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<% for post in @posts %>
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<p><%= link_to(post.title, :action => "show", :id => post.id) %></p>
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<% end %>
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weblog/show.html.erb:
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<p>
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<b><%= @post.title %></b><br/>
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<b><%= @post.content %></b>
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</p>
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weblog/new.html.erb:
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<%= form "post" %>
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This simple setup will list all the posts in the system on the index page,
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which is called by accessing /weblog/. It uses the form builder for the Active
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Record model to make the new screen, which in turn hands everything over to
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the create action (that's the default target for the form builder when given a
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new model). After creating the post, it'll redirect to the show page using
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an URL such as /weblog/5 (where 5 is the id of the post).
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== Download
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The latest version of Action Pack can be found at
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* http://rubyforge.org/project/showfiles.php?group_id=249
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Documentation can be found at
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* http://api.rubyonrails.com
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== Installation
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You can install Action Pack with the following command.
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% [sudo] ruby install.rb
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from its distribution directory.
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== License
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Action Pack is released under the MIT license.
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== Support
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The Action Pack homepage is http://www.rubyonrails.org. You can find
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the Action Pack RubyForge page at http://rubyforge.org/projects/actionpack.
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And as Jim from Rake says:
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Feel free to submit commits or feature requests. If you send a patch,
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remember to update the corresponding unit tests. If fact, I prefer
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new feature to be submitted in the form of new unit tests.
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