GA Lecture Notes

Wk1_Tue(Day2).md

tl;dr: Ruby Arrays,

Objectives:MVC & Testing , Arrays & Functions ,Networking & HTTP

Ruby "Strings" vs. [Arrays]

array: an Object with ordered storage container

```Ruby names = ["Travis", "Megan", "Tod", "Bryan"] #literal array- what you see is what you get, also json (JS object notation) #json simply means a literal array that can be copied & pasted into other programs require "json" names.methods().sort() # gives you all the methods available to your array & json names.to_json #=> "[\"Travis\", \"Megan\", \"Tod\", \"Bryan\"]" ``` ```bash j@ubuntu~$ ~/.rvm/ j@ubuntu~$ find ~/.rvm/ j@ubuntu~$ find ~/.rvm/ | grep 'array' ```

More on Strings & Arrays

```Ruby var = "hi there" var[2] #=> ' ' var[-1] #=> 'e' #last character on your string var.inspect #=> "\"hi there\"" # \\ escapes the string var.class #=> String var.class.ancestors #=> [String, Comparable, Object, Kernel, BasicObject] ``` Numbers: ```ruby num1 = 42 num2 = 42.0 num1.class = Fixnum num2.class = Float **because of this, anything that deals with money, operate the math by multiplying 100 then divide by 100 when you're done with it PEMDAS - Parens, Exponents, Multiplication, Division, Addition, Subtraction ex. 2+((3*4) / (2**3)) ``` Truth/False: In Ruby, only "nil" and "false" are falsey. This is not the case in other languages. ```ruby if 0 puts "this is true" #=> this is true if false puts "false" #=> false

*truthy: "Strings", true, " ", everything else *falsey: nil, false

true || true #=> true true || false #=> false false|| false #=> false

In ruby, it is good practice to default something to nil then assign something value to it later on.


bash$ gem install pry  

  => This goes to rubygems.org online to download the "pry" gem


Book: Ruby under a microscope

<strong>Naming convention:</strong>

Use snake_case for methods and variables.

Use CamelCase for classes and modules. (Keep acronyms like HTTP, RFC, XML uppercase.)

Use SCREAMING_SNAKE_CASE for other constants.

The names of predicate methods (methods that return a boolean value) should end in a question mark. (i.e. Array#empty?).

The names of potentially "dangerous" methods (i.e. methods that modify self or the arguments, exit!, etc.) should end with an exclamation mark. Bang methods should only exist if a non-bang method exists. (More on this).



<h4>Homework Review:</h4>    
```Ruby
#!/usr/bin/env ruby

# 1. create a literal array of all the names in class
# 2. Accept '-g' or 'n'
# 3. Accept a number for either
# 4. when you get '-g x', split the array into 'x' groups and print them
# 5. when you get '-n x', print out 'x' names

# Bonus 1- Store/ retrieve the array in a json file

# Bonus 2- Keep track of selected names

names = %w[Josh Kevin Travis Dave Kristine Donielle Lauren
  	    Megan Xiao Sharif Theo Ricky Justin Ian Ryan Brian  
		                               Alex Elen Lior Tod Karl]
puts "Class size is #{names.length}"

	method = ARGV[0]
	num    = ARGV[1].to_i

	if '-g' == method
		puts
		puts "Dividing class into #{names.length/num} groups of #{num}'s:"
		puts
		p names.shuffle.each_slice(num).to_a
		#p xx is equivalent to puts xx.inspect (prints the value of 
                #inspect instead of to_s, suitable for debugging)

	elsif '-n' == method
		puts "selecting #{num} random number of peeps:"
		p names.sample(num)

	else
		puts "Error. Check your input."
	end	

Cheap Tricks:

*Xmodmap - to change your keyboard to Dvorak vs. Querty

*While in Terminal, to get to beginning of line: Ctrl + a; to get to end of line: Ctrl + e

*for Mac- if you're running into issues opening a non-mac program, press Appl Ctrl then mouse click on the icon to open that way.