wk04_day01.md

Week 04, Day 01

24 / 08 / 2015

What we covered today:

• Warmup Exercise
  • Solution
• RVM and Ruby installation guide
• Ruby
  • Data Types
  • Variables
  • Conditionals
  • Control Structures
  • Methods (Functions in JS)

How to get Ruby

Install Developer Tools from Xcode (this should have happened for most of you)

xcode-select --install

Access a specific URL using a secured line and run the downloaded program

curl -sSL https://get.rvm.io | bash -s stable

Restart the terminal, and try running the command rvm.

If it doesn't work...

• Open the bash_profile up in Sublime

  subl ~/.bash_profile

• Add these lines into the bottom of the bash_profile and save it

  [[ -s "$HOME/.rvm/scripts/rvm" ]] && source "$HOME/.rvm/scripts/rvm"

  export PATH="$PATH:$HOME/.rvm/bin"

Restart the terminal again

rvm

rvm list known

rvm get stable --auto

Go here and find the most recent version - https://www.ruby-lang.org/en/downloads/

Latest version at the time of writing was 2.2.2, swap those in for the latest stable version that shows on that website

rvm install ruby-2.2.3

rvm --default use 2.2.3

Let's test that it has all worked.

• ruby -v
• rvm -v
• which ruby - should not return anything in the /usr/local/bin
• which rvm

If all of this has worked, run...

gem install pry

Common Commands

ruby -v - Will return the current version of Ruby

which ruby - What is the path to the version of Ruby you are using

ruby hello_world.rb - Runs the hello_world.rb file

irb - Runs a ruby console

pry - Runs a better console

<CTRL> + D - Ends a file in irb or ruby

Data Types

Strings

Again, delimited by quotes.

"string" 'string'

Numbers

There are multiple types:

• Integer (Fixnum)
• Float
• Bignum

Logical Operators

Lots of them, but the basic ones are:

+= - Add then assign -= - Minus then assign *= - Multiply then assign /= - Divide then assign ** - To the power of

Comparison Operators

All the same ones...

>
>=
<
<=
== # Normally stick to two equals in Ruby
===

<=> (returns -1 if less than, 0 if equal, and 1 if greater than)
etc.

Variables

No need for the var keyword.

ruby = "is nice"

Much harder to make global variables, it isn't the default behaviour in Ruby

Methods (Functions in JS)

puts "this is like console.log print "this is also like console.log p "this is a bit more complex

Brackets are mostly optional, occasionally necessary (only in method or function chaining)

puts("this is like console.log)

Basic Naming Conventions

snake_case_everywhere - very rare to see camelCase!

Variable Interpolation in Strings

Interpolation just means you can put code inside

name  = "gilberto"
drink = "scotch"

"My name is #{ name } and I drink #{ drink }!"
# A lot nicer than "my name is " + name + " and I drink " + drink
# Which is the way you would do it in JS

Interpolation only works with double quotes!! Single quotes means leave this string alone, this is mine

Comments in Ruby

# This is is a single line comment

# This is
# a multiline
# comment

# OR (don't do this)

=begin
This is also a multi line comment
You can't have any an empty line between the =begin and the start of the comment
=end

Getting User Input

In JS, we have prompt etc.

# Initial greeting
puts "What is your first name?"

# first_name = gets
# This will wait for user input, and include the new line in the variable

first_name = gets.chomp
# This will wait for user input, and strip the new line from the variable
# For more documentation on chomp - http://ruby-doc.org/core-2.2.0/String.html#method-i-chomp

puts "Your first name is #{ first_name }."

puts "What is your surname?"
surname = gets.chomp
puts "Your surname is #{ surname }."

puts "Your full name is #{ first_name } #{ surname }"
# fullname = "#{ first_name } #{ surname }"
# Sames as ... puts "Your full name is #{ fullname }"

puts "What is your address?"
address = gets.chomp
puts "Your name is #{ fullname } and you live at #{ address }"

# INTERPOLATION ONLY WORKS ON DOUBLE QUOTES!

Conditionals

IF STATEMENTS

if 13 > 10
    p "Yep, it is a bigger number"
end

grade = "A"

if conditional
    # To do
elsif conditional
    # To do
else
    # To do
end

p "Yep, it is a bigger number" if 13 > 10 # This only works in single line statements

# It's called a modifier (if modifier)

UNLESS STATEMENTS

x = 1
unless x > 2
    puts "x is less than 2"
else
    puts "x is greater than 2"
end

code_to_perform unless conditional

CASE STATEMENTS

Think of these as shorter if statements, but don't overuse them (particularly in JS)

grade = 'B'
case grade
when 'A'
    p 'Great Job'
when 'B'
    p 'Good Job'
when 'C'
    p 'Adequate Job'
else
    p 'Talk to the Hand'
end

case expression_one
when expression_two, expression_three
    statement_one
when expression_four, expression_five
    statement_two
else
    statement_three
end

# Very similar to the switch statement in Javascript!

Now that we know this stuff, give these exercises a go.

WHILE LOOPS

while conditonal
    statement
end

while true
    p "OMG"
end # BAD IDEA

i = 0
while i < 5
    puts "I: #{ i }"
    i += 1
end

UNTIL LOOPS

until conditional
    statement
end

i = 0
until i == 5
    puts "I: #{ i }"
    i += 1
end

ITERATORS

So, so common in Ruby.

5.times do
    puts "OMG"
end

5.times do |i|
    puts "I: #{ i }"
end
# The thing that times wants to pass into me is stored as the parameter between the pipe characters

5.downto(0) do |i|
    puts "I: #{ i }"
end

FOR LOOPS (No one ever uses these)

# Don't ever use them

for i in 0..5
   puts "I: #{ i }"
end

Generating Random Numbers

Random.rand # Generates a number between 0 and 1
Random.rand(10) # Generates a random number up to 10 (including zero and 10)
Random.rand(5..10) # Generates a number between 5 and 10 (also includes them)
Random.rand(5...10) # Does not include 5 and 10

Now that you know this stuff, have a crack at these exercises.

Methods or Functions

def hello
    # A plain method
end

hello # called like this

def hello( name )
    # A plain method that takes a parameter
    # When calling this, you MUST pass in a parameter or it will throw an error
end

hello "Wolf"    # Called this way
hello("Wolf")   # Or this

def hello( name = "World" )
    # A function with a default parameter
    # This won't throw an error in the case that you don't pass a parameter in
end

hello           # Works this way
hello("Wolf")   # Or this

Methods in Ruby have an implicit return, meaning that you don't need to actually use the return keyword, it does it automatically.

Parentheses are optional!

Here is the homework for tonight!