mvc & activerecord by christian mohr & mohamed souiai

MVC & ActiveRecord

by Christian Mohr & Mohamed Souiai

Content

• MVC

• ActionController

• ActionView

• ActiveRecord

• Routing

Model View Controller

•Architectural pattern for interactive Applications.

•Isolates business logic from user interface consideration.

•Grants flexibility modularity reusability of Objects.

Model

• In general the model represents the information (the data) of the application and the business rules used to manipulate the data.

• Inside Ruby on Rails the ActiveRecord Module corresponds to the model in the MVC paradigm.

View

• In general the view corresponds to elements of the user interface such as text, checkbox items.

• In Rails the ActionView is used to create Templates and visualizes the data provided by the controller, in different formats.

Controller

• In general the controller manages details involving the communication to the model of user actions such as keystrokes and mouse movements.

• In Rails the Controller is realized by the ActionController who coordinates the interaction between user and Application.

Control center ActionController

Tasks:• Receiving Http-Request data (i.e. Form data)• Database requests via model-classes.• Setting and query of cookies and sessions.• Setting flash messages.• Calling templates.• Forwarding Files and data.• Authentication .


Our Controller class inherits from the ApplicationController.Class AirportsController < ApplicationController

UML Diagram:


Controller generator:Syntax:ruby script/generate controller name [action_1 …

action_N]

Generates the controller app/controllers/name_controller.rb with optional actionsand ActionViews: app/views/name/action_n.html.erb.

The Actions can be added manually. In that case, the corresponding views are not generated automatically.

1,2


Controller Actions:

• The public Methods of the Controller• Access via URL call:

http://<host>:<port>/<controller>/<action>

3,4,5

ActionView

• Template-File containing Ruby- and HTML-Code.

• By Convention, the name is the same as the corresponding action.

• All View-Files have the extension .html.erb

ActionView

Syntax in ActionView Files

Ruby Code: <% … code … %>

Ruby Output: <%=output%>

By using html_escape(…) or h(…) Tag-specific characters (i.e. <, > and &) are masked.

ActionView

Instance variables:

Variables with a leading ‘@’ are accessible to all methods inside the defining controller and the corresponding views .

ActiveRecord

… treating Data from a Database like Objects

• Domain Specific Language (DSL)

“ActiveReord” Design pattern by Martin Fowler:Mapping object-oriented Data to relational Data

and vice versa.

ActiveRecordModels:Classes, that

represent a data- table and are responsible for the database operations (CRUD)

Each row in the database represents a model-object

ActiveRecord

Model-Generator Syntax:

ruby script/generate model modelname

Generates the ActiveRecord model file app/models/modelname.rb

To create a new Row in the data table, we create a new Object of the class modelname.

By Convention, the data table name is lower case and plural and the model class name is in singular with upper case initial.

6

ActiveRecord

CRUD (Create, Read, Update Delete)The four basic database operations:• Create create a new dataset• Read read a dataset• Update alter an existing dataset• Delete delete a dataset

ActiveRecord

ActiveRecord-Classes provide methods for the following basic database operations:

• new creates a new ActiveRecord-Object• Create(…) creates and saves a new AR-Object• Find(ID) finds the correspoding dataset• Find(:all, :conditions=>…)

It is possible to add custom methods.7,8

ActiveRecord

ActiveRecord-Objects offer the following methods:

• save saving an object to the database• update alter all or single object attributes• destroy delete an object

ActiveRecord

Interesting Functions:• Validation• Before- and After-Filter• Associations and Relations• Migrations• Transactions• Automatic attributes (created_at, updated_at)

ActiveRecord

• Oracle• PostgreSQL• SQLite• Sybas

Supported relational management database systems

• DB2• Firebird• Frontbase• MySQL• Openbase

Routing

• Defines which internal controller and action should be called depending on the URL.

• Routing rules are stored in config/routes.rb• Auto generated entries:ActionController::Routing::Routes.draw do |map| # ... map.connect ':controller/:action/:id' map.connect ':controller/:action/:id.:format'end

• Restart the server after changing the Routing!

Routing

Routing Diagram

Routing

LinksTo generate a Link to

http://localhost:3000/bookmarks/show/1

The code in the View would look like this:<%= link_to "show bookmarks", :controller => 'bookmarks',:action => "show", :id => 1 %>

There are ways to simplify this!

Routing

Simplified URL’s using map.connect• Given Routing:

http://localhost:3000/authentication/login• Desired URL:

http://localhost:3000/loginAdd routing-entry above standard entries:map.connect 'login', :controller =>

"authentication”, :action => "login"

Routing

Named Routes using map.nameAdd routing-entry above standard entries:map.login 'login', :controller =>

"authentication", :action => "login"

Provides login_url and login_path

• name_url contains absolute path incl. host• name_path contains relative path without host.

Routing

root route using map.root• An applications default index page URL:

http://localhost:3000/applicationname• If no controller provided (i.e. http://localhost:3000)

the default rails welcome-page is displayed• changing config/routes.rb entry tomap.root :controller => "bookmarks”

makes bookmarks the root controller• Make sure to delete homonymous files in pubic/

Routing

Also possible:

• Complex routing with regular expressions• Routing with defined HTTP-Method

(GET, POST, PUT, DELETE)

The end

Thank you for listening.

mvc & activerecord by christian mohr & mohamed souiai

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