• Setup Digital server, Nginx host rails, apache2 host PHPMYADMIN
• Update gem:
  gem install rubygems-update
update_rubygems
gem update --system

  (if not work, try gem update `gem outdated | cut -d ' ' -f 1`)

• Throw an exception manually :raise ....
• Handle Photo and Album (kylehuynhphotography.com): click here
• Clear the assets
  rake assets:clobber (remove /home/rails/tmp/cache/assets)
rake assets:clean
• Check the error log in kylehuynhphotography.com:
  cat /var/log/nginx/access.log
• Validate string field is unique

validates :title, :uniqueness => true

• Validating image url format as png, jpeg or gif

validates :image_url, :format => {
:with => %r{A.(gif|jpg|png)/z}i,
:message => ‘must be a URL for GIF, JPG or PNG image.’
}

• Link to images in css, let’s say you store all of images in the directory :/assets/images/cusdir/image.png

background-image:url(“/assets/nobile/cusdir/image.png”)

• Reset database from rails command :

rake db:reset

• Validating number field compare with number value

validates :price, :numericality => {:greater_than_or_equal_to => 0.01}

• For (i=0; i< no; i++) in Ruby :

no.times do |p|

…

end

• Generate model from Rails command :

rails generate scaffold Product
title:string description:text image_url:string price:decimal 
Then, rake db:migrate

• Remove scaffold model from Rails command:

 rails destroy scaffold Product

• rails generate scaffold Product will create table Products with id as default primary key. In order to ignore primary key automatically creating, passing id: false

create_table :products, id: false do |t|
t.string :name, null: false
end

• Instance variable in ruby class

• • @@variable_name = “hello world”
  • call under def : puts @@variable_name

• In the case that you already created table, create a migration class to modify table by the following:

class AddPkPhotoid < ActiveRecord::Migration
def change
remove_column :photos, :id
add_column :photos, :photo_id, :primary_key
end
end

• Parse json and store it to a string variable

require ‘json’
require ‘open-uri’
@json = JSON.parse(open(“..Flickr api url…”).read)

• Add unique validation for 1 or mutiple column for table

validates_uniqueness_of :photo_id

validates_uniqueness_of :photo_id, :scope => :album_id

• Modifying column for table by Rails command

change_column :set_photos, :setphoto_id, :string

•  Generate controller by Rails command:

rails generate controller Say hello goodbye