Rails 3 Beginner to Builder 2011 Week 2

Beginner to Builder
Week 2
Richard Schneeman
@schneems

June, 2011
Thursday, June 16, 2011

Rails - Week 2
• Ruby
• Hashes & default params
• Classes
• Macros
• Methods
• Instances
• Methods
@Schneems

Rails - Week 2
• Code Generation
• Migrations
• Scaﬀolding
• Validation
• Testing (Rspec AutoTest)

@Schneems

Ruby - Default Params
def what_is_foo(foo = "default")
puts "foo is: #{foo}"
end

what_is_foo
>> "foo is: default"

what_is_foo("not_default")
>> "foo is: not_default"

@Schneems

Ruby
• Hashes - (Like a Struct)
• Key - Value Ok - Diﬀerent
DataTypes
Pairs

hash = {:a => 100, “b” => “hello”}
>> hash[:a]
=> 100
>> hash[“b”]
=> hello
>> hash.keys
=> [“b”, :a]
@Schneems

• Hashes in method parameters
• options (a hash) is optional parameter
• has a default value
def list_hash(options = {:default => "foo"})
options.each do |key, value|
puts "key '#{key}' points to '#{value}'"
end
end
list_hash
>> "key 'default' points to 'foo'"
@Schneems

def list_hash(options = {:default => "foo"})
options.each do |key, value|
puts "key '#{key}' points to '#{value}'"
end
end
list_hash(:override => "bar")
>> "key 'override' points to 'bar'"
list_hash(:multiple => "values", :can => "be_passed")
>> "key 'multiple' points to 'values'"
>> "key 'can' points to 'be_passed'"

@Schneems

Hashes in Rails
• Used heavily as parameters
• options (a hash) is optional parameter

Rails API: (ActionView::Helpers::FormHelper) text_area
@Schneems

Ruby
• Objects don’t have attributes
• Only methods
• Need getter & setter methods

@Schneems

Attributes
class MyClass
def my_attribute=(value)
@myAttribute = value
end
def my_attribute
@myAttribute
end
end
>> object = MyClass.new
>> object.my_attribute = “foo”
>> object.my_attribute
=> “foo”
@Schneems

Ruby - attr_accessor
class Car
attr_accessor :color
end

>> my_car = Car.new
>> my_car.color = “hot_pink”
>> my_car.color
=> “hot_pink”

@Schneems

Ruby - Self
class MyClass
puts self
end
>> MyClass # self is our class

class MyClass
def my_method
puts self
end
end
MyClass.new.my_method
>> <MyClass:0x1012715a8> # self is our instance

@Schneems

Ruby - Class Methods
class MyClass
def self.my_method_1(value)
puts value
end
end
MyClass.my_method_1("foo")
>> "foo"

@Schneems

Ruby - Class Methods
class MyClass
def self.my_method_1(value)
puts value
end
end
my_instance = MyClass.new
my_instance.my_method_1("foo")
>> NoMethodError: undefined method `my_method_1' for
#<MyClass:0x100156cf0>
from (irb):108
from :0

def self: declares class methods
@Schneems

Ruby - Instance Methods
class MyClass
def my_method_2(value)
puts value
end
end
MyClass.my_method_2("foo")
>> NoMethodError: undefined method `my_method_2' for
MyClass:Class
from (irb):114
from :0

@Schneems

Ruby - Instance Methods
class MyClass
def my_method_2(value)
puts value
end
end
my_instance = MyClass.new
my_instance.my_method_2("foo")
>> "foo"

@Schneems

Ruby
• Class Methods class Dog

• Have self def self.find(name)
...
• Instance Methods end

• Don’t (Have self) def wag_tail(frequency)
...
end
end

@Schneems

Ruby
• attr_accessor is a Class method
class Dog
attr_accessor :fur_color
end

Can be deﬁned as:
class Dog
def self.attr_accessor(value)
#...
end
end

@Schneems cool !

Scaffolding
• Generate Model, View, and Controller &
Migration

>> rails generate scaffold
Post name:string title:string content:text

• Generates “One Size Fits All” code
• app/models/post.rb
• app/controllers/posts_controller.rb
• app/views/posts/ {index, show, new, create,
destroy}
• Modify to suite needs (convention over
conﬁguration)
@Schneems

Database Backed Models
• Store and access massive amounts of
data
• Table
• columns (name, type, modiﬁer)
• rows
Table: Users

@Schneems

Create Schema
• Create Schema
• Multiple machines

Enter...Migrations
@Schneems

Migrations
• Create your data structure in your Database
• Set a database’s schema
migrate/create_post.rb
class CreatePost < ActiveRecord::Migration
def self.up
create_table :post do |t|
t.string :name
t.string :title
t.text :content
end
SystemSetting.create :name => "notice",
:label => "Use notice?", :value => 1
end
def self.down
drop_table :posts
end
end

@Schneems

Migrations
• Get your data structure into your database

>> rake db:migrate

• Runs all “Up” migrations
def self.up
t.string :name
t.string :title
t.text :content
end
end
@Schneems

Migrations
def self.up
• Creates a Table named post def self.up
t.string :name do |t|
• Adds Columns
create_table :post
t.string :title
t.string :name
t.string :title
• Name, Title, Content t.textt.text :content
end
:content

end end
• created_at & updated_at
added automatically end

@Schneems

Migrations
• Active Record maps ruby objects to database
• Post.title

Active Record is Rail’s ORM
def self.up
t.string :name
t.string :title
t.text :content
end
end

@Schneems

Migrations
• Made a mistake? Issue a database Ctrl + Z !

>> rake db:rollback

• Runs last “down” migration

def self.down
drop_table :system_settings
end

@Schneems

Rails - Validations
• Check your parameters before save
• Provided by ActiveModel
• Utilized by ActiveRecord
class Person < ActiveRecord::Base
validates :title, :presence => true
end

bob = Person.create(:title => nil)
>> bob.valid?
=> false
>> bob.save
=> false

@Schneems

Rails - Validations
Can use ActiveModel without Rails
class Person
include ActiveModel::Validations
attr_accessor :title
validates :title, :presence => true
end

bob = Person.create(:title => nil)
>> bob.valid?
=> false
>> bob.save
=> false

@Schneems

Rails - Validations
• Use Rail’s built in Validations
# :acceptance => Boolean.
# :confirmation => Boolean.
# :exclusion => { :in => Enumerable }.
# :inclusion => { :in => Enumerable }.
# :format => { :with => Regexp, :on => :create }.
# :length => { :maximum => Fixnum }.
# :numericality => Boolean.
# :presence => Boolean.
# :uniqueness => Boolean.

• Write your Own Validations
class User < ActiveRecord::Base
validate :my_custom_validation
private
def my_custom_validation
self.errors.add(:coolness, "bad") unless self.cool == “supercool”
end
end

@Schneems

If & Unless
puts “hello” if true
>> “hello”
puts “hello” if false
>> nil

puts “hello” unless true
>> nil
puts “hello” unless false
>> “hello”

@Schneems

blank? & present?
puts “hello”.blank?
>> false
puts “hello”.present?
>> true
puts false.blank?
>> true
puts nil.blank?
>> true
puts [].blank?
>> true
puts “”.blank?
>> true

@Schneems

Testing
• Test your code (or wish you did)
• Makes upgrading and refactoring easier
• Diﬀerent Environments
• production - live on the web
• development - on your local computer
• test - local clean environment

@Schneems

Testing
• Unit Tests
• Test individual methods against known
inputs
• Integration Tests
• Test Multiple Controllers
• Functional Tests
• Test full stack M- V-C
@Schneems

Unit Testing
• ActiveSupport::TestCase
• Provides assert statements
• assert true
• assert (variable)
• assert_same( obj1, obj2 )
• many more

@Schneems

Unit Testing
• Run Unit Tests using:
>> rake test:units RAILS_ENV=test

@Schneems

Unit Testing
• Run Tests automatically the
background
• ZenTest
• gem install autotest-standalone
• Run: >> autotest

@Schneems

Questions?

@Schneems

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Rails 3 Beginner to Builder 2011 Week 2