Read "Dynamo, Amazon’s Highly Available Key-value Store" Read "Bigtable, A Distributed Storage System for Structured Data" Read "Streaming Systems" 3, Watermarks Read "Streaming Systems" 1&2, Streaming 101 Read "F1, a distributed SQL database that scales" Read "Zanzibar, Google’s Consistent, Global Authorization System" Read "Spanner, Google's Globally-Distributed Database" Read "Designing Data-intensive applications" 12, The Future of Data Systems IOS development with Swift Read "Designing Data-intensive applications" 10&11, Batch and Stream Processing Read "Designing Data-intensive applications" 9, Consistency and Consensus Read "Designing Data-intensive applications" 8, Distributed System Troubles Read "Designing Data-intensive applications" 7, Transactions Read "Designing Data-intensive applications" 6, Partitioning Read "Designing Data-intensive applications" 5, Replication Read "Designing Data-intensive applications" 3&4, Storage, Retrieval, Encoding Read "Designing Data-intensive applications" 1&2, Foundation of Data Systems Three cases of binary search TAMU Operating System 2 Memory Management TAMU Operating System 1 Introduction Overview in cloud computing 2 TAMU Operating System 7 Virtualization TAMU Operating System 6 File System TAMU Operating System 5 I/O and Disk Management TAMU Operating System 4 Synchronization TAMU Operating System 3 Concurrency and Threading TAMU Computer Networks 5 Data Link Layer TAMU Computer Networks 4 Network Layer TAMU Computer Networks 3 Transport Layer TAMU Computer Networks 2 Application Layer TAMU Computer Networks 1 Introduction Overview in distributed systems and cloud computing 1 A well-optimized Union-Find implementation, in Java A heap implementation supporting deletion TAMU Advanced Algorithms 3, Maximum Bandwidth Path (Dijkstra, MST, Linear) TAMU Advanced Algorithms 2, B+ tree and Segment Intersection TAMU Advanced Algorithms 1, BST, 2-3 Tree and Heap TAMU AI, Searching problems Factorization Machine and Field-aware Factorization Machine for CTR prediction TAMU Neural Network 10 Information-Theoretic Models TAMU Neural Network 9 Principal Component Analysis TAMU Neural Network 8 Neurodynamics TAMU Neural Network 7 Self-Organizing Maps TAMU Neural Network 6 Deep Learning Overview TAMU Neural Network 5 Radial-Basis Function Networks TAMU Neural Network 4 Multi-Layer Perceptrons TAMU Neural Network 3 Single-Layer Perceptrons Princeton Algorithms P1W6 Hash Tables & Symbol Table Applications Stanford ML 11 Application Example Photo OCR Stanford ML 10 Large Scale Machine Learning Stanford ML 9 Anomaly Detection and Recommender Systems Stanford ML 8 Clustering & Principal Component Analysis Princeton Algorithms P1W5 Balanced Search Trees TAMU Neural Network 2 Learning Processes TAMU Neural Network 1 Introduction Stanford ML 7 Support Vector Machine Stanford ML 6 Evaluate Algorithms Princeton Algorithms P1W4 Priority Queues and Symbol Tables Stanford ML 5 Neural Networks Learning Princeton Algorithms P1W3 Mergesort and Quicksort Stanford ML 4 Neural Networks Basics Princeton Algorithms P1W2 Stack and Queue, Basic Sorts Stanford ML 3 Classification Problems Stanford ML 2 Multivariate Regression and Normal Equation Princeton Algorithms P1W1 Union and Find Stanford ML 1 Introduction and Parameter Learning

Rails tutorial by Ihower


File structure:

  • app/
    • app/controllers
    • app/models
    • app/views
    • app/helpers
    • app/assets
  • config/
  • db/ : schema and migrations
  • doc/
  • lib/ : load files with require
    • lib/task/
  • log/
  • public/
  • bin/
  • test/
  • tmp/
  • vendor/assets


# generate
rg model person
rg controller people

# open console
rc production # with production environment
rc --sandbox # sandbox mode

# open server
rs -p 4000 -e production # set port and environment

# new rails project
bin/rails new my_app --database=mysql # create MyApp project in ./my_app

# open db console

# destroy

start and application settings

application.rb has timezone setting.

other settings

In config/initializers.

$ rails c
$ Loading development environment (Rails 3.2.8)
$ > "Business".singularize  => "Busines" #
$ > "moose".pluralize => "mooses"  #

Model and migration

create model

rails g model event name:string description:text is_public:boolean capacity:integer

apply db changes

bin/rake db:migrate

modify model

rails g migration add_status_to_events
# in the migration
class AddStatusToEvents < ActiveRecord::Migration
  def change
    add_column :events, :status, :string

validation of info

class Event < ActiveRecord::Base
    validates_presence_of :name


match route

put as the last line, match path “/foo/bar” to Controller foo Action bar

    match ':controller(/:action(/:id(.:format)))', :via => :all

list all

The instance variable “@foo” will be passed to view to be used.

def index
  @events = Event.all

new action

def new
  @event =

new view

<%= form_for @event, :url => { :controller => 'events', :action => 'create' } do |f| %>
    <%= f.label :name, "Name" %>
    <%= f.text_field :name %>

    <%= f.label :description, "Description" %>
    <%= f.text_area :description %>

    <%= f.submit "Create" %>
<% end %>

It will send parameters to create Action by params (a Hash)

def create
  @event =
  # add input validation, so can try again
    redirect_to :action => :index
  # go to the template instead of calling action, information is saved
    render :action => :new
  flash[:notice] = "event was successfully created"


# to check the params, filter to have `params[:event][:name]`
# and `params[:event][:description]`  
def event_params
  params.require(:event).permit(:name, :description)

show individual record

If go to http://localhost:3000/events/show/1', Rails will call show Action and set params[:id] = 1`

def show
  @event = Event.find(params[:id])
  # set page title
  @page_title =

edit record

def edit
  @event = Event.find(params[:id])

Then edit view

<%= form_for @event, :url => { :controller => 'events', :action => 'update', :id => @event } do |f| %>
    <%= f.label :name, "Name" %>
    <%= f.text_field :name %>

    <%= f.label :description, "Description" %>
    <%= f.text_area :description %>

    <%= f.submit "Update" %>
<% end %>

Then update Action

def update
  if @event.update(event_params)
    redirect_to :action => :show, :id => @event
    render :action => :edit
  flash[:notice] = "event was successfully updated"


destroy record

def destroy
  @event = Event.find(params[:id])
  flash[:alert] = "event was successfully deleted"

  redirect_to :action => :index


Page layout

Default: views/layouts/application.html

add flash notice before yield in default layout

<p style="color: green"><%= flash[:notice] %></p>
<p style="color: red"><%= flash[:alert] %></p>

Partial template

The name starts with a _ like _form.html.erb

# _form
<%= f.label :name, "Name" %>
<%= f.text_field :name %>

<%= f.label :description, "Description" %>
<%= f.text_area :description %>

# new view
<%= form_for @event, :url => { :controller => 'events', :action => 'create' } do |f| %>
    <%= render :partial => 'form', :locals => { :f => f } %>
    <%= f.submit "Create" %>
<% end %>

# edit view
<%= form_for @event, :url => { :controller => 'events', :action => 'update', :id => @event } do |f| %>
    <%= render :partial => 'form', :locals => { :f => f } %>
    <%= f.submit "Update" %>
<% end %>

before action


class EventsController < ApplicationController
  before_action :set_event, :only => [ :show, :edit, :update, :destroy]
  # ....
  def set_event
    @event = Event.find(params[:id])

multi pages

  1. add gem "kaminari" to Gemfile
  2. bundle install

add to index Action

def index
  @events =[:page]).per(5)

edit index view

<%= paginate @events %>


event_path(@event) /events/1 show action   /events/1 update action /events/1 destroy action
events_path /events index action /events create action    
edit_event_path(@event) /events/1/edit edit action      
new_event_path /events/new new action      
  1. show, new, edit, destroy are operations on single element.
  2. index and create are operations on sets
  3. event_path(@event) need parameters, decide show, update or destroy based on HTTP verb
  4. events_path doesn’t need parameters, decide index or create based on HTTP verb.
## add to routes.rb
resources :events

modify CRUD

# show
<%= link_to "Show", event_path(event) %>
# edit
<%= link_to 'Edit', edit_event_path(event) %>
# delete
<%= button_to 'Delete', event_path(event), :method => :delete, :data => { :confirm => "Are you sure?" } %>
# back to index
<p><%= link_to 'Back to index', events_path %></p>
# new view: send to
<%= form_for @event, :url => events_path do |f| %>
# edit view: send to
<%= form_for @event, :url => event_path(@event), :method => :patch do |f| %>

# event controller
# create
redirect_to events_url
# update
redirect_to event_url(@event)

Creative Commons License
Melon blog is created by melonskin. This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
© 2016-2020. All rights reserved by melonskin. Powered by Jekyll.