sk187/intro_to_rails.md

## intro_to_rails.md

      
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              intro_to_rails.md
            
          
    Welcome Intro to Ruby on Rails!


Hi! I'm...


Sung Kim


I'm a software engineer & data scientist at Booz Allen Hamilton.


I'm @Quant_LIfe on Twitter but sk187 just about just everywhere else.


Agenda


What is programming? (briefly)
Intro to ruby
Intro to object-oriented programming
Intro to rails


What is programming?

When you tell someone to make a sandwich, your job is made much easier because they already know what a sandwich is.

If you were to tell your computer to make a sandwich you would have to give very specific directions.

open cabinet
see if there is bread
if there is no bread go to the store and buy bread
open bread packaging and take out 2 slices


Programming is telling your computer how to do something.  Large tasks must be broken up into smaller tasks, which must be broken up into even smaller tasks, down until you get to the most basic tasks that you don't have to descibe - and that your computer already knows how to do.

Programming Languages

In order to tell your computer how to do something, you must use a programming language.

... that's where ruby comes into play!

What is Ruby?

Ruby is a object oriented pogramming language that is simple, easy to learn, and elegant.
	5.times do 
    	  puts "Hi, there!"
	end
See?

What is Ruby on Rails?

It is a framework built with ruby and uses ruby to build websites

Handles web requests
Easily configures to any database
makes best practice assumptions so that we don't have to


Getting started with ruby

We are going to be using Ruby REPL
Here are the code examples: Code along

Let's create our first program!

	puts "what is your name?"
	name = gets.chomp
	puts "Hi #{name}, how are you??"

Intro to Ruby


Data Types

Integer
String
Boolean
Symbols
Array
Hash


Programming Basics

Variables
Methods
Classes


Primative Data Types

Integer = some number
x = 1
x.class
# => Fixnum

x = 1.75
x.class
# => Float
String = letters
x = 'Sung'
x.class
# => String
Boolean = True or False
x = true
x.class
# => TrueClass 

Primative Data Types (continued)

Symbol = immutable values used often for keys in a hash
x = {}
x[:symbol] = 1 
x[:symbol]
# => 1 

Variables

x = 1
x # => 1

sung = "Engineer"
sung # => Engineer

Methods

Methods are a lot like variables.
You save values to variable names like
you save certain instructions to method names
def count(x)
	i = 1
	while i < x+1
		puts i
		i +=1
	end
end

count(5)
1
2
3
4
5
#=> nil

Collections: Arrays and Hash

Arrays are ordered lists of values starting at 0
array = ['a','b','c']
array[0]
# => a
Hashes are unordered key value pairs (Kind of like a dictionary)
hash = {a: 1, b: 2, c: 3}
hash.keys
# => [:a, :b, :c]
hash.values
# => [1, 2, 3]
hash[:a]
# => 1

Dictionary Sort

Instructions:
Prompts user to enter a word

Tells user to enter another word or hit the return key
Repeats that process until the user hits the return key
Returns all the words entered in alphabetical order


Intro to Object Oriented


Objects are basic building blocks of Ruby
Literally everything is an object in Ruby
You can think of Objects as any noun (users, computers , animals, cars, pets, houses, etc..etc)


There are two steps to creating an object in ruby
The first is to define a class

Class

Classes are basically your blueprint or a template for your object
class Person
	def initialize(name)
		puts "A user is being created"
	end
end
A class can be used to create many objects

The second step is to instantiate the object (aka create your object from the class)
person1 = Person.new('Sung')
person2 = Person.new('Tesla')

Anatomy of a class

class ClassName
end
class definition starts with the keyword class followed by the class name
and is delimited with end

Initialize method

class Box
	def initialize(w,h)
		@width = w
		@height = h
	end
end
The initialize method is considered our constructor.  It is used when you want to initialize class variables at the same time as creating your class

Instance variables

@width = w
@height = h
instance variables are class attributes and become properties of the object when an object is instanciated.  They can also be passed between all of the class methods

#Accessor methods
# define a class
class Box

	# constructor method
	def initialize(w,h)
		@width, @height = w, h
	end

	# accessor methods
	def printWidth
		@width
	end

	def printHeight
		@height
	end
end

# create an object
box = Box.new(10, 20)

# use accessor methods
x = box.printWidth
y = box.printHeight
Accessor methods allow us to access our instance variables from outside of the class

Intro to Rails (and websites in general)


Question 1 - What is Ruby on rails?


Open Source Framework
Built with and uses the ruby programming language
Uses MVC framework (model, view. controller)


Let's talk a little bit about databases

Two "General Types" Sql and NoSql

###SQL
-Excel like with rows and columns
###No SQL
-some type of data store, like a JSON Object
	Person1 {
		name: 'Sung',
		job: ['Software Engineer', 'Instructor'],
		languages: ['Korean', 'English', 'French', 'Japanese'],
		planguages: ['Ruby', 'Python', 'Javascript']
	}

Let's just jump into and build something cool!
First


Download Postgresql for Heroku and Rails Postgresql
Start your postgres server by running the GUI app

gem install rails


Useful commands

rails new [name of app] -d postgresql #creates a new rails app
rails generate scaffold [model name] [field:datatype] 
	#generates the rails scaffold 

rake db:create #creates a new database 
rake db:migrate #migrates over the database schema from ruby land to sql land
rails s #starts the rails server


Deploying to Heroku


Download Homebrew for Git or install git by itself

-ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
homebrew git #to intall git

OR

Git Homepage
Create an account on Heroku
In your console pointed to the folder with your app,

git init # This starts Git 
git add . # This adds all files that have been changed
git commit -m "initial commit" # This saves all of the files you added with git add
gem install heroku # This installs the Heroku gem to so you can do Heroku CLI commands
heroku login # To pass authentication credentials 
heroku create # Adds a Heroku remote to your git
git remote -v # To check on all remotes for your git 
git push [remote name][branch name] # Pushes your local git code to a remote
git push heroku master # Publishes your local code to the Heroku Server
heroku open # Opens the website