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<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Intro to Ruby ~ Girl Develop It</title>
<meta name="description" content="This is the official Girl Develop It Core Intro to Ruby course. The course is meant to be taught in five two-hour sessions. Each of the slides and practice files are customizable according to the needs of a given class or audience.">
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</head>
<body>
<div class="reveal">
<!-- Any section element inside of this container is displayed as a slide -->
<div class="slides">
<section>
<img src="images/gdi_logo_badge.png">
<h3>Intro to Ruby</h3>
<h3>Class 3</h3>
</section>
<section>
<h3>Welcome!</h3>
<div class = "left-align">
<p>Girl Develop It is here to provide affordable and accessible programs to learn software through mentorship and hands-on instruction.</p>
<p class ="green">Some "rules"</p>
<ul>
<li>We are here for you!</li>
<li>Every question is important</li>
<li>Help each other</li>
<li>Have fun</li>
</ul>
</div>
</section>
<!-- Homework Review - 10 min -->
<section>
<h3>Homework Discussion</h3>
<p>How was last week's homework? Do you have any questions or concepts that you'd like to discuss?</p>
</section>
<section>
<h3>grandma.rb</h3>
<pre><code contenteditable class="ruby">
chatting = true
byes = 0
while chatting
puts "Ask Grandma a question:"
said = gets.chomp!
if said == "BYE"
byes += 1
if byes > 2
chatting = false
else
puts "** Grandma is ignoring you **"
end
elsif said == said.upcase
year = 1930 + Random.rand(20)
puts "NO, NOT SINCE #{year}!"
else
puts "HUH?! SPEAK UP, SONNY!"
end
end
puts "Thanks for chatting with Grandma"
</code></pre>
</section>
<section>
<h3>leap.rb</h3>
<pre><code contenteditable class="ruby">
puts "Enter a starting year in the format YYYY"
starting = gets.chomp!.to_i
puts "Enter an ending year in the format YYYY"
ending = gets.chomp!.to_i
puts "LEAP YEARS between #{starting} and #{ending}"
starting.upto(ending) do |year|
divisible_by_4 = (year % 4) == 0
not_divisible_by_100 = (year % 100) != 0
divisible_by_400 = (year % 400) == 0
is_leap_year = (divisible_by_4 && not_divisible_by_100)
|| divisible_by_400
if is_leap_year
puts "#{year}"
end
end
</code></pre>
</section>
<section>
<h3>Review</h3>
<ul>
<li class="fragment">Conditions - if, elsif, else</li>
<li class="fragment">Loops - while, for</li>
<li class="fragment">Arrays - [1,2,3] or %w(one two three)</li>
<li class="fragment">Hashes - {"one" => 1, "two" => 2}</li>
</ul>
</section>
<section>
<h3>What we will cover today</h3>
<ul>
<li class="fragment">Methods</li>
<li class="fragment">Objects</li>
<li class="fragment">Object Oriented Programming</li>
</ul>
</section>
<section>
<h3>Methods</h3>
<p>A <strong>method</strong> is a name for a chunk of code</p>
<p class="fragment">Methods are often used to define reusable behavior.</p>
<p class="fragment">Let's look at a method we've already used:</p>
<pre><code contenteditable class="fragment ruby">
1.even?
=> false
"fred".capitalize
=> "Fred"
</code></pre>
<p>If you have some code you want to reuse or organize, methods will help.</p>
</section>
<section>
<h3>Let's Develop It!</h3>
<p>Find the methods available on <a href="http://www.ruby-doc.org/core-2.1.0/String.html">String</a> and <a href="http://www.ruby-doc.org/core-2.1.0/Integer.html">Integer</a></p>
<p>Do they have any similar methods?</p>
<pre><code contenteditable class="fragment ruby">
"abc".next
=> "abd"
"abz".next
=> "aca"
1.next
=> 2
-1.next
=> 0
</code></pre>
</section>
<section>
<h3>Write a Method</h3>
<p>Let's write a method together</p>
<p><strong>def</strong> means define</p>
<p><strong>subtract</strong> is the name of the method</p>
<p><strong>x, y</strong> are parameters</p>
<p><strong>x - y</strong> is the body of the method</p>
<p><strong>x - y</strong> is also the return value</p>
<pre><code contenteditable class="fragment ruby">
def subtract x, y
x - y
end
</code></pre>
</section>
<section>
<h3>Let's Develop It!</h3>
<p>Let's write a method that takes in a number and tells us if it is even.</p>
<p>Hint: if number % 2 == 0, then it is even</p>
<pre><code contenteditable class="fragment ruby">
def method_name(parameter)
# method implementation
end
</code></pre>
</section>
<section>
<h3>Method Return Value</h3>
<p>Every Ruby method returns something.</p>
<p>Usually, it's the last statement in the method.</p>
<p>It could be the value sent to <strong>return</strong> if that came first.</p>
<pre><code contenteditable class="fragment ruby">
def subtract(x,y)
x - y
'another thing'
end
return_value = subtract(5, 2)
puts return_value
def subtract(x,y)
return x - y
'another thing'
end
return_value = subtract(5, 2)
puts return_value
</code></pre>
</section>
<section>
<h3>Arguments vs. Parameters</h3>
<p>Technically speaking, arguments are passed and parameters are declared.</p>
<p>Note that the variable names don't have to match!</p>
<p>In this code, 5 is an argument and x is a parameter</p>
<pre><code contenteditable class="fragment ruby">
def subtract(x,y)
x - y
end
subtract(5, 2)
</code></pre>
</section>
<section>
<h3>Splat Arguments</h3>
<pre><code contenteditable class="fragment ruby">
def greet(greeting, *names)
names.each do |name|
puts "#{greeting}, #{name}!"
end
end
>> greet("Hello", "Alice", "Bob", "Charlie")
Hello, Alice!
Hello, Bob!
Hello, Charlie!
</code></pre>
</section>
<section>
<h3>Default Values</h3>
<pre><code contenteditable class="fragment ruby">
def eat(food = "chicken")
puts "Yum, #{food}!"
end
>> eat
Yum, chicken!
>> eat "bananas"
Yum, bananas!
</code></pre>
</section>
<section>
<h3>Default Hash Parameter</h3>
<pre><code contenteditable class="fragment ruby">
def add_to_x_and_y(amount, vals)
x = vals[:x]
y = vals[:y]
x + y + amount
end
add_to_x_and_y(2, {:x => 1, :y => 2})
# same as...
add_to_x_and_y 2, :x => 1, :y => 2
# same as...
add_to_x_and_y 2, x: 1, y: 2
# same as...
add_to_x_and_y 2, y: 2, x: 1
</code></pre>
</section>
<section>
<h3>Named Parameters</h3>
<p>To pass variable parameters, or to pass named parameters, you can use an options hash</p>
<pre><code contenteditable class="fragment ruby">
bake("Wheat")
bake("Sourdough", :flour => "sour")
bake("Pumpernickel", :creamer => "butter")
def bake(name, options = {})
flour = options[:flour] || "rye"
creamer = options[:creamer] || "cream"
puts "baking a nice #{flour} loaf with #{creamer}"
end
</code></pre>
</section>
<section>
<h3>Methods & Variables</h3>
<p><strong>Local vars</strong> are only available in the methods where they were defined.</p>
<pre><code contenteditable class="fragment ruby">
# Let's extract the length of the padded string into
# a local variable
def message(our_string)
length = 80
puts our_string.center(length, "-")
end
def different_message(some_string)
puts our_string.center(length, "=")
end
</code></pre>
</section>
<section>
<h3>Objects</h3>
<p>An <strong>Object</strong> is the building block of a program.</p>
<p class="fragment">Objects <strong>do things</strong> and have <strong>properties</strong>.</p>
<pre><code contenteditable class="fragment ruby">
Object: Number
What can it do?
- Add
- Subtract
- Divide
- Multiply
What are some properties of your Number?
- Length
- Base
- Even
</code></pre>
</section>
<section>
<h3>Object Class</h3>
<p><strong>Objects</strong> can be grouped by Class.</p>
<p class="fragment">Classes define a template for objects. They describe what a certain type of object can do and what
properties they have in common.
</p>
<p>There are many kinds of objects, including String, Number, Array, Hash, Time, ...</p>
<p>To create an object we use .new</p>
<pre><code contenteditable class="fragment ruby">
array = []
array = Array.new
</code></pre>
<p>now array refers to an object instance</p>
</section>
<section>
<h3>Object Methods</h3>
<p>Methods can be defined on objects.</p>
<pre><code contenteditable class="fragment ruby">
array = Object.new
def array.delete
puts "deleted the array"
end
array.methods(false)
</code></pre>
</section>
<section>
<h3>Instance Variables</h3>
<p>Represent object state</p>
<p>Names start with an @</p>
<p>Only visible inside the object</p>
<pre><code contenteditable class="fragment ruby">
cookie = Object.new
def cookie.add_chips(num_chips)
@chips = num_chips
end
def cookie.yummy?
@chips > 100
end
cookie.add_chips(500)
cookie.yummy? #=> true
</code></pre>
</section>
<section>
<h3>Object Oriented Programming</h3>
<ul>
<li class="fragment">Object Oriented Programming is one of many <strong>programming approaches</strong>: procedural, event-driven, functional,
declarative...
</li>
<li class="fragment">These days, most programming is done in an OO language: Java, C#, C++.</li>
<li class="fragment">All this means is that programs are <strong>organized around objects</strong> (data & methods).</li>
<li class="fragment">You might choose OOP because Objects make things <strong>easier to understand</strong> and act as a natural way to modularize code.
When a large code base is composed of many small Objects, it is <strong>easier to maintain</strong> and change.
</li>
</ul>
</section>
<section>
<h3>OOP & Easy Understanding</h3>
<p>Objects often take on names from their domain which makes them easy to conceptualize.</p>
<p>For example, without seeing my code, you can probably guess what a Bike object can do (or not do)</p>
</section>
<section>
<h3>OOP & Encapsulation</h3>
<p>One thing that makes code easier to maintain is Encapsulation which is one of the fundamentals of OOP.</p>
<p><strong>Encapsulation</strong> is a nice way of saying 'put all my properties/behaviors in my capsule where other
objects can't touch them'.
</p>
<p>By assigning certain responsibilities to objects, code is more purposeful and less likely to be changed by
accident.
</p>
</section>
<section>
<h3>OOP & Inheritance</h3>
<p>Just as you inherited traits from your mom, your objects may inherit traits from other objects.</p>
<p><strong>Inheritance</strong> is when you use one class as the basis for another.</p>
<p>You might use Inheritance if two objects have the same properties and methods. This way you don't need to write the
same thing twice.
</p>
<pre><code contenteditable class="fragment ruby">
class MyString < String
end
my_string = MyString.new
my_string.upcase
</code></pre>
</section>
<section>
<h3>OOP & Polymorphism</h3>
<ul>
<li>Similar to inherited traits and behaviors, there are also polymorphic traits and behaviors.</li>
<li><strong>Polymorphic</strong> means many forms.</li>
<li>Within OOP, this relates to different objects being able to respond to the same message in different ways.</li>
</ul>
<pre><code contenteditable class="fragment ruby">
[1, "abc"].each {|object| puts object.next}
</code></pre>
</section>
<section>
<h3>Questions?</h3>
</section>
<section>
<h3>Homework</h3>
<p><strong>Practice:</strong> Do some of the exercises at the end of <a href="http://pine.fm/LearnToProgram/?Chapter=08" alt="Chp 8 of Learn to Program">Chapter 8</a> of Learn to Program.</p>
<p><strong>Prep:</strong> Read <a href="http://pine.fm/LearnToProgram/?Chapter=09" alt="Chp 9 of Learn to Program">Chapter 9</a> of Learn To Program- don't try to do the exercises at the end yet, though.</p>
</section>
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Intro to Ruby
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