rb-intro/slides.md

% Introduction to Ruby % Peter Jones <pjones@devalot.com> %

Introduction

* Slide Time: 00:02 (00:02) * Please ask questions at any time. * Your job is to understand the material. * My job is to keep us on track and on time.

30-second History of Ruby

• When and where?
• Influences.
• “Modern” Ruby.

* Slide Time: 00:02 (00:04) * First released in 1995 by Japanese Programmer "Matz". * Syntax influenced by Perl (C-style). * Features influenced by Smalltalk and Lisp. * Modern Ruby began with v1.9 (2007) * Several Implementations, main is [MRI] [].

What is Ruby?

* Slide Time: 00:05 (00:09) * Purely object-oriented. * General purpose (not just web apps!) * Dynamically typed. * Garbage collected.

Ruby Syntax

* Slide Time: 00:08 (00:17) * Perl-flavored, C-like syntax * Semicolons are optional (line-based) * Whitespace insignificant. * Constants use CamelCase * Variables and methods use snake_case. * Blocks of code are delimited by `begin...end` or `do...end`. * All methods return a value (no `void` functions). * Implicit return of final value. * The scope of a variable is determined by its name.

Everything is an Object

Consider this irb session:

1.class
"Hello World".class

* Slide Time: 00:02 (00:19) * Numeric literals are objects. * String literals are objects.

Everything is an Object: Assignment

Open irb and experiment with the following:

• Numeric literals.
• String literals.
• true and false
• (0..10).class

* Slide Time: 00:06 (00:25)

Everything is an Expression

* Slide Time: 00:02 (00:27) * An `if` statement is really an expression. * Using `if` in string interpolation. * Class definition is an expression. * Method definition is an expression. * Loading a file is an expression.

Everything is an Expression: Assignment

Open irb and let’s play with some expressions together.

* Slide Time: 00:05 (00:32) * `if true then "hello" end` * `if false then "hello" end`

Object-oriented Programming

* Slide Time: 00:05 (00:37) * Ruby only allows single inheritance. * Multiple inheritance is emulated with modules. * Modules *are not* interfaces.

Everything is an Object (Part 2)

Consider this irb session:

String.class
anon = Class.new do
  def hello; "hi"; end
end;nil
object = anon.new;nil
object.hello

* Slide Time: 00:05 (00:42) * Even classes are objects! * Creating classes at runtime.

Blocks and Iterators

* Slide Time: 00:03 (00:45) * Blocks are borrowed from Smalltalk. * Blocks can be used as iterators (`Array#each`).

Blocks and Iterators: Assignment

Open irb and play with long- and short-form blocks.

* Slide Notes: 00:08:00 (00:53:00) * Long form: `do |x| ... end`. * Short form: `{|x| ... }`.

Blocks and Resource Management

* Slide Notes: 00:04 (00:57) * And also for resource management (`File::open`). * You can write methods which accept blocks. * Blocks can be passed around from method to method.

Closing

Open irb and ask some questions!

* Slide Time: 00:03 (01:00)