Building your app (1) Modeling the data Raymond van Dongelen | NHL | www.webxy.nl

Modeling the data

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

Contents Datamodel ActiveRecord Sample application

Datamodel

ActiveRecord

Sample application

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”

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

Sample application User Project Task Subtask User can be in many projects Project can have many users A project has many tasks A task has many subtasks Sample can be found on http://www.webxy.nl/?p=63