MVC

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MVC ActiveRecord

• by Christian Mohr Mohamed Souiai

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Content

• MVC
• ActionController
• ActionView
• ActiveRecord
• Routing

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Model View Controller

• Architectural pattern for interactive
  Applications.
• Isolates business logic from user interface
  consideration.
• Grants flexibility modularity reusability of
  Objects.

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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.

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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.

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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.

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A simple bookmark projekt

• In the following slide we introduce the MVC
  paradigm in the context of Ruby on rails.

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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 .

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Control center ActionController
UML Diagram
Our Controller class inherits from the
ApplicationController. Class AirportsController lt
ApplicationController
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Control center ActionController

• Controller generator
• Syntax
• ruby script/generate controller name action_1
  action_N
• Generates the controller app/controllers/name_con
  troller.rb
• with optional actions
• and ActionViews app/views/name/action_n.html.er
  b.
• The Actions can be added manually.
• In that case, the corresponding views are not
  generated automatically.

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Control center ActionController

• Controller Actions
• The public Methods of the Controller
• Access via URL call
• http//lthostgtltportgt/ltcontrollergt/ltactiongt

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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

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ActionView

• Syntax in ActionView Files
• Ruby Code lt code gt
• Ruby Output ltoutputgt
• By using html_escape() or h() Tag-specific
  characters (i.e. lt, gt and ) are masked.

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ActionView

• Instance variables
• Variables with a leading _at_ are accessible to
  all methods inside the defining controller and
  the corresponding views .

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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.

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ActiveRecord

• Models
• Classes, that represent a data- table and are
  responsible for the database operations (CRUD)
• Each row in the database represents a model-object

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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.

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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

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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, conditionsgt)
• It is possible to add custom methods.

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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

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ActiveRecord

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

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ActiveRecord
Supported relational management database systems

• Oracle
• PostgreSQL
• SQLite
• Sybas

• DB2
• Firebird
• Frontbase
• MySQL
• Openbase

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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
• ActionControllerRoutingRoutes.draw do map
• ...
• map.connect 'controller/action/id'
• map.connect 'controller/action/id.format'
• end
• Restart the server after changing the Routing!

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Routing
Routing Diagram
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Routing

• Links
• To generate a Link to
• http//localhost3000/bookmarks/show/1
• The code in the View would look like this
• lt link_to "show bookmarks", controller gt
  'bookmarks',
• action gt "show", id gt 1 gt
• There are ways to simplify this!

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Routing

• Simplified URLs using map.connect
• Given Routing
• http//localhost3000/authentication/login
• Desired URL
• http//localhost3000/login
• Add routing-entry above standard entries
• map.connect 'login', controller gt
  "authentication, action gt "login"

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Routing

• Named Routes using map.name
• Add routing-entry above standard entries
• map.login 'login', controller gt
  "authentication",
• action gt "login"
• Provides login_url and login_path
• name_url contains absolute path incl. host
• name_path contains relative path without host.

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Routing

• root route using map.root
• An applications default index page URL
• http//localhost3000/applicationname
• If no controller provided (i.e.
  http//localhost3000)
• the default rails welcome-page is displayed
• changing config/routes.rb entry to
• map.root controller gt "bookmarks
• makes bookmarks the root controller
• Make sure to delete homonymous files in pubic/

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Routing

• Also possible
• Complex routing with regular expressions
• Routing with defined HTTP-Method
• (GET, POST, PUT, DELETE)

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The end

• Thank you for listening.