Rails (1) Modelling the data Raymond van Dongelen | NHL | www.webxy.nl

Modelling the data

MVC Model-view-controller (MVC) is a software architecture that separates an application's data model, user interface, and control logic into three distinct components so that modifications to one component can be made with minimal impact to the others. Seperate data from decisions from view Create maintainable applications Let each layer perform tasks it is best at

Model-view-controller (MVC) is a software architecture that separates an application's data model, user interface, and control logic into three distinct components so that modifications to one component can be made with minimal impact to the others.

Seperate data from decisions from view

Create maintainable applications

Let each layer perform tasks it is best at

Model The data that is needed for the application The data is transient (is saved between sessions) Closely related to databases

The data that is needed for the application

The data is transient (is saved between sessions)

Closely related to databases

Controller Makes important decisions Controls traffic

Makes important decisions

Controls traffic

View Displays information Handles small events

Displays information

Handles small events

Scaffolding Ruby generates standard functionality for your application, including a models, views and controllers You adapt it

Ruby generates standard functionality for your application, including a models, views and controllers

You adapt it

Datamodel Should prevent storing the same information twice Should guard relations in the data Should be able to cope with changing data structure

Should prevent storing the same information twice

Should guard relations in the data

Should be able to cope with changing data structure

Ruby and data All database handling is done in the model Powerful features to validate data, guard relations, search data. All data is wrapped in Ruby classes SQL is almost never needed

All database handling is done in the model

Powerful features to validate data, guard relations, search data.

All data is wrapped in Ruby classes

SQL is almost never needed

Ruby naming Table name plural Key in a table “id” Reference to another table “table_id”

Table name plural

Key in a table “id”

Reference to another table “table_id”

Relations belongs_to has_one has_and_belongs_to_many has_many

belongs_to

has_one

has_and_belongs_to_many

has_many

Let’s rock Like we never done before...

Like we never done before...

ActiveRecord(1) Validators: validates_presence_of validates_uniqueness_of Relations: belongs_to has_one has_and_belongs_to_many has_many

Validators:

validates_presence_of

validates_uniqueness_of

Relations:

belongs_to

has_one

has_and_belongs_to_many

has_many

ActiveRecord(2) Example: class Agenda < ActiveRecord::Base belongs_to :user validates_presence_of :user, :message => &quot;cannot be empty&quot; end

Example:

class Agenda < ActiveRecord::Base

belongs_to :user

validates_presence_of :user, :message => &quot;cannot be empty&quot;

end

ActiveRecord (3) @agenda = Agenda.find(1) puts (@agenda.user.name) <== We are able to display the user, it is automatically fetched

@agenda = Agenda.find(1)

puts (@agenda.user.name)

<== We are able to display the user, it is automatically fetched

ActiveRecord (4) Dynamic find Agenda.find_all_name (“Home”) User.find_all_by_email (“ [email_address] ”)

Dynamic find

Agenda.find_all_name (“Home”)

User.find_all_by_email (“ [email_address] ”)

ActiveRecord (5) Many many powerful features Read chapter 14 agile web development with Ruby on Rails

Many many powerful features

Read chapter 14 agile web development with Ruby on Rails

Example db