Ruby For Kids For Dummies®
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Copyright © 2016 by John Wiley & Sons, Inc., Hoboken, New Jersey
Published simultaneously in Canada
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Library of Congress Control Number: 2015941961
ISBN 978-1-119-05590-7 (pbk); ISBN 978-1-119-05599-0 (ebk); ISBN 978-1-119-05600-3
Ruby For Kids For Dummies is an introduction to the basics of coding using the Ruby programming language. In each chapter, I walk you through a step-by-step set of instructions to create a Ruby program for your Mac or Windows computer. You don’t need to have any programming experience to understand this book, but you do need to have a sense of curiosity and adventure!
The Ruby programming language has been around since the mid-1990s and has become very popular with web application programmers. It can be used for so much more than just web apps. In this book, you’ll see that you can use Ruby for small “command line” tools and calculations; larger programs for home, work, or school; or even graphical games (and I’ll show you a lot of games).
Ruby was designed by its creator Yukihiro Matsumoto to be both fun and productive. My hope is that as you explore the projects in this book, you’ll definitely have fun and be inspired to continue to use Ruby (or any other programming language) to realize your own coding ideas.
Programming in general is similar to sports, music, or even creative arts. It’s hard to just absorb a book on the subject and expect to understand it completely or start to gain mastery of the topic. Instead, you need to have keyboard time and practice. Even professional coders continue to practice throughout their careers.
By exploring and playing around with the projects here, you’ll be taking the first steps down a really interesting Ruby-colored road.
Programming is a large topic, and Ruby itself is a very powerful language. I’ll be working to shed light on some of the more fundamental parts of Ruby and coding in general. There is no rush to finish the projects in the book. Go through each Ruby For Kids For Dummies project as quickly or slowly as you like. Each chapter’s project is a self-contained useful utility or fun game. Along the way, you’ll learn how to use the very same tools that the professionals use, and learn the kinds of techniques that will help you grow as a programmer.
You don’t need to have any previous programming experience, but if you know a little, that’s fine — you’ll pick up how Ruby does things and also see some similarities to other languages. I’ll show you the “Ruby way” when applicable, but I’ll also show the easy way when you’re just learning the concepts.
Topics covered in this book include the following:
Learning to program with Ruby isn’t just about writing code in the language. You also need to learn about the tools, resources, and community that stand behind the language.
Ruby has become so popular because it’s a relatively simple language to learn, and the tools needed to write Ruby, test it, and run it are widely available and free. In this book, I help you get started with just a few basic, free, programs that do everything you need to create some pretty sophisticated pieces of software.
You’ll also learn about general programming techniques, and most important, see a wide variety of projects that will pique your interest and hopefully encourage you to take your exploration to the next level.
To make this book easier to read, you’ll want to keep in mind a few tips. First, all Ruby code and all terminal commands appear in monospaced type like this:
puts "hello programs! Welcome to Ruby"
The margins on a book page don’t have the same room as your monitor likely does, so long lines of Ruby and any output it creates may break across multiple lines. Remember that your computer sees such lines as a single line of Ruby. I show that everything should be on one line by breaking it at a punctuation character or space and then indenting any overage, like so:
def room_type
["cave", "treasure room", "rock cavern", "tomb", "guard room", "lair"].sample
end
Ruby is case sensitive, which means that swapping the use of uppercase or lowercase letters or a combination of the two can break things. In order to make sure that you get the correct results from the projects in the book, always stick to the same capitalization and spelling that I use.
Ruby also cares about the kind of quotation marks that you use! So, if you see double quotes (") or single quotes ('), be sure to use what I show and make sure they’re straight and not curly.
To understand programming, you need a bit of patience and the ability to think logically about a topic. You don’t need to be a computer guru or a hacker. You don’t need to be able to build a computer or take one apart (although that might be fun!). You don’t need to know a bit from a byte or how many programmers it takes to screw in a new light bulb.
However, I do need to make some assumptions about you. I assume that you can turn your computer on, that you know how to use a mouse and a keyboard, and that you have a working Internet connection and web browser. You should also know how to find and launch programs on your computer.
In this book, I explain everything else you need to get set up and coding in Ruby.
Here’s a list of the icons I use in this book to flag text and information that’s especially noteworthy.
The Technical Stuff icon highlights technical details that you may or may not find interesting. Feel free to skip this information, but if you’re the techie type, you might enjoy reading it.
The Tip icon highlights helpful tips that show you easy ways or shortcuts that will save you time or effort.
Whenever you see the Remember icon, pay close attention. You won’t want to forget the information you’re about to read — or, in some cases, I remind you about something that you’ve already learned that you may have forgotten.
Be careful. The Warning icon warns you of pitfalls to avoid.
I’ve put together a lot of extra content that you won’t find in this book. Go online to find the following:
www.dummies.com/cheatsheet/rubyforkids. Here, you find information on basic Ruby statements, conditions, loops and objects; a list of words that can’t be used as Ruby variables or methods; a list of some of the useful methods provided by common Ruby classes; descriptions of common errors and what may cause them; and some small snippets of useful Ruby.www.dummies.com/extras/rubyforkids. In these articles, I cover things like good ways to organize your Ruby class, some common Ruby shortcuts (also called “idiomatic Ruby”), Ruby troubleshooting tips, and more.Programming is a blast, and doubly awesome with Ruby. Even Ruby’s creator wants you to have fun! After you learn the basics, you’ll start to find all kinds of things you can do with your newfound powers.
I’m very interested to hear how it goes as you learn Ruby! If you want to show me your new ideas, bug fixes, or enhancements to my projects, or if you have programs you come up with on your own, you can do so on Facebook (www.facebook.com/mobirobo), on Twitter (www.twitter.com/mobirobo_inc), or via email at ruby@mobirobo.com.
Part I
In this part …
Getting Started with Ruby
Big Numbers
Bigger Hello World
For Dummies can help you get started with lots of subjects. Visit www.dummies.com to learn more and do more with For Dummies!
Project 1
Computers are almost everywhere today — from laptops, tablets, or phones, to TVs, watches, medical devices, kitchen appliances, cars, spaceships, big factories, little robots, and millions of other places large and small.
How do computers know what to do inside all these things? Someone has to teach them! Behind every cool animated movie, website, game, vehicle, or device, someone has worked hard to instruct a computer on how to perform its task. That person was a programmer.
In this chapter, I give you a little background about programming and how programmers organize their thoughts when writing computer software or code. I share some background about Ruby, the programming language I cover throughout this book. Then I tell you how to install the tools you’ll use for all the projects in the rest of the book.
Computers are kind of dumb by themselves. Without a person to tell it exactly what to do, a computer will just sit there. Everything a computer does — and I mean everything, from the display of pictures and text on a screen, to the understanding of what you type on a keyboard or touch and swipe on a tablet — requires some software to interpret signals coming through the various circuits in one part of the computer and modify and send them to the right place in another part to get something done. That’s a lot of work!
Fortunately, over the years, many smart people have come up with different ways to communicate clearly with computers. Writing instructions for a computer is called programming or coding, and the end result is a program or software.
A computer programming language shares many similarities to a human language. It has symbols and words (like nouns and verbs) that you put together following a syntax (rules for spelling, order, and punctuation).
When you start learning to program, you open up a wide world in which you can apply this knowledge when working with any technology that uses computers. You’ll be able to read other people’s programs to learn more about computers or to use code you write to solve homework problems, create puzzles, build a new game, create a website, or even control machines like robots.
Programs needs to be very precise in order to instruct a computer to do something. Imagine that you want to tell your friend to do something. For instance, how would you tell someone to sit down in a desk chair? You might say:
Your friend is smart enough that your instructions make perfect sense, and she’ll sit on the chair safely without falling over or anything crazy like that. People have a lot of knowledge they can use to interpret instructions like this.
Now, if you have to tell a computer to sit down, what would that be like? You have to be a lot more exact. For example, you would have to say:
Even these instructions might not be enough for a computer because they make some assumptions (like what your body parts are called).
Try it yourself: How would you tell a computer exactly how to do something like filling a glass with water?
Programmers need to think in this very detail-oriented way. As you learn to write computer programs, you’ll get good at breaking a problem down into smaller and smaller parts. Each of those parts will eventually be a line of code that you create. Over time, you’ll learn other techniques that help you identify the different objects you’ll need to describe to the computer and the actions those objects will take. This will help you organize your code in ways that make it possible to create very sophisticated software. Pretty cool, huh?
There are many different computer programming languages out there. Each language has strengths and weaknesses. Some languages are easier if you’re trying to control large machines. Some languages are specialized for mobile apps — the kind on an iPhone, for example. Some languages make it easy to create websites. And some languages are for doing science and engineering.
A general-purpose programming language is good for many different kinds of projects. There are many general-purpose programming languages to choose from. The important thing when you’re wanting to learn programming is to pick something and dive into training yourself to think like a programmer. When you learn one programming language, learning another one is much, much easier.
In this book, I use the language Ruby. Ruby is a flexible, general-purpose language that is useful for many kinds of projects. It was created in the mid-1990s in Japan by Yukihiro Matsumoto (best known by his nickname, “Matz”). Don’t worry — you don’t have to learn Japanese to program with Ruby! Today Ruby is used around the world for all kinds of projects, by beginners and professionals alike.
Matz had a wonderful philosophy in mind when creating Ruby: He wanted programmers to be productive, enjoy programming, and be happy. This is one of my favorite things about Ruby: As you learn it and write programs, you’ll have fun!