razorcd

# Returns a User instance that's not saved (does not write to DB)
user = build(:user)

# Returns a saved User instance (writes to DB)
user = create(:user)

# Returns a hash of attributes that can be used to build a User instance
attrs = attributes_for(:user)

# Returns an object with all defined attributes stubbed out

razorcd

== - returns true only if the two compared entities are the same object
=== - is the Case Equality Operator (Case Subsumption Operator) (fits in drawer?)
eql? - method returns true if obj and other have the same value.
equal? - determines object identitfy. Compares pointers

razorcd

MySQL

Getting started:

• http://www.sqlteaching.com/
• https://www.codecademy.com/courses/learn-sql

Related tutorials:

• MySQL-CLI: https://www.youtube.com/playlist?list=PLfdtiltiRHWEw4-kRrh1ZZy_3OcQxTn7P
• Analyzing Business Metrics: https://www.codecademy.com/learn/sql-analyzing-business-metrics

razorcd

exec("echo 'hello world'") # exits from ruby, then runs the command
system('echo', 'hello world') # returns the status code
sh('echo', 'hello world') # returns the status code
`echo "hello world"` # returns stdout
%x[echo 'hello world'] # returns stdout

razorcd

1. Codebase
One codebase tracked in revision control, many deploys

2. Dependencies
Explicitly declare and isolate dependencies

3. Config
Store config in the environment

4. Backing services

razorcd

- Single Responsability - classes and methods should handle/do only one thing. Methods max 5 lines long, classes max 100 lines long.
- Open Closed - classes should be open for extension and closed for change
- Liskov Substitution - Having a main class and a subclass. Anywhere we use the main we should get same result by using the subclass.
- Interface Segragation - no client should be forced to depend on methods it does not use. Maybe class does not do only one thing? Split the class in more classes (and maybe add a facade).
- Dependency Inversion - Dont tight couple the classes by creating one instance inside another class. Inject them as dependencies when calling the method outside the class.  
                         Use `A.new(b: B.new(5))` instead of `A.new(5)` where `class A; def initialize(i); @b= B.new(i); end`

- Law of Demeter - don't chain methods that could be changed in future. (except when methods returns self)
- Don't repeat yourself - reuse code

razorcd

//simple

var var1 = 1;
var func1 = function(input) {
	//var var2 = 2;
	return input + var1; // + var2;
}

console.log(func1(1));
console.dir(func1);

razorcd

1. install openjdk
  `sudo apt-get install openjdk-7-jdk`
  
2. install `android sdk`
  # download android sdk
  wget http://dl.google.com/android/android-sdk_r24.2-linux.tgz
  
  tar -xvf android-sdk_r24.2-linux.tgz
  cd android-sdk-linux/tools

razorcd

Check free mem:
free -m

Add swap:
```
  sudo dd if=/dev/zero of=/swap bs=1M count=1024
  sudo mkswap /swap
  sudo swapon /swap
```

razorcd

# Class Specialisations  (Composition + Dependency injection)

class House
  DATA = [1,2,3,4,5,6]
  attr_reader :data

  def initialize(orderer: DefaultOrderer.new, formatter: DefaultFormatter.new)
    # @data = formatter.format(orderer.order(DATA))
    formatted_data = formatter.format(DATA)
    @data = orderer.order(formatted_data)