- hackety
- beginner
Hello there!
Let's get started
Welcome to your first lesson in Ruby! You're going to have a blast.
Ruby is a great programming language that you can use to make all kinds of things with. Let's get going!
A bit more about Ruby
Konnichiwa, Ruby!
Ruby was created by
まつもと ゆきひろ
(you can just call him Matz) in 1995. If you couldn't guess, Matz is from Japan. Here he is:
Ruby is enjoyable
Matz has this to say about Ruby:
I hope to see Ruby help every programmer in the world to be productive, and to enjoy programming, and to be happy. That is the primary purpose of Ruby language.
One more thing about Ruby: Rubyists (that's what people who like Ruby call themselves) have a saying: MINSWAN. This stands for Matz Is Nice So We Are Nice. Which is a pretty nice saying, itself. Be nice to everyone, and give them a hand when they need it!
Displaying Things
Let's do this!
Okay! The very first thing that you need to know is how to show something on the screen. Otherwise, you won't know what's going on!
In order to start coding, we need to bring up the Editor. Its icon looks like this:
Click the icon to open the Editor up, and then we'll move on...
Hello, World!
There are two ways of doing this. Here's the first: alert
alert "Hello, world!"
Type this in and press the 'Run' button.
alert
Okay, let's break this down: There's two main parts to this little program: you
have an alert, and a "Hello, world!". These two parts work just like an
English sentence: The alert is a verb and the stuff in the ""s is an object.
In Ruby, we call verbs methods. The alert verb says 'Put an alert box on
the screen, and the content of the box is whatever thing you give me.'
We'll talk about the "Hello, world!" in just a second. Here's the other way of
making this happen:
puts "Hello, world!"
But if you try that here, it won't work! The puts method doesn't display a
dialog box, it puts text out to a command-line prompt. Since Hackety Hack is all
graphical, this doesn't work here. So we'll be using alerts throughout these
tutorials, but if you look at other Ruby tutorials, you may see puts.
Letters, words, and sentences
Strings
Okay! Now that you've got that verb bit down, it's time to learn about Strings. Strings are what we call a bunch of words between a pair of " characters. The "s are used to tell the computer what words you actually want to say. Let's think about our example:
alert "Hello, world!"
If you didn't have the "s, the computer wouldn't know which words were methods and which ones were part of the string! And consider this:
alert "I am on high alert!"
Without making all of those words a string, how would Ruby know that the second alert was some text you wanted to say, rather than another alert box?
Adding Strings
Now, if you want to put two bits of strings together, you can use the +
character to do it. Try typing this:
alert "Hello, " + "world!"
Same thing! The + sticks the two strings together. This will end up being
super useful later!
Numbers and Math
Numbers
You can just use numbers, and Ruby understands them:
alert 2
You can even use numbers that have a decimal point in them:
alert 1.5
Basic Math
You can also do math with numbers, and it'll work out pretty well:
alert 1 + 2
alert 5 - 3
alert 2 * 3
alert 4 / 2
But if you try this, nothing happens:
alert "hey" + 2
This is kind of fun and silly, though:
alert "hey" * 2
Errors
You know how nothing happened when you hit the Run button earlier? That was because there was an error. You can see any errors that run by hitting either Alt-/ or Command-/, depending on what kind of computer you're using.
The error that results from alert "hey" + 2 is
can't convert Fixnum into String
What is that?
A few words about types
Why's it do that?
Each part of a Ruby program is an Object. Right now, all you need to know
about Objects is that it's sort of like saying "a thing." Your program is made
up of a bunch of Objects working together.
We'll learn more about Objects in a future lesson, but there is one thing I'll
tell you: Objects have a 'type.' This lets Ruby know what kind of Object it
is.
Adding numbers to words
That's why
alert "hey" + 2
doesn't really work: "hey" is a String object, and 2 is a Fixnum object. And
adding Strings and Fixnums doesn't make any sense. We can make this code
work, though!
All we need to do is turn the Fixnum into a String. We can do this by using
the to_s method.
alert "hey" + 2.to_s
Let's look at that again
alert "hey" + 2.to_s
Okay, this isn't bad. We have our alert method. We're giving it "hey" +
2.to_s. The 2.to_s turns a Fixnum 2, which is like the mathematical idea of
a 2, into the String 2, which is like when you write a 2 down on a piece of
paper.
Variables
They're like boxes
What happens if we want to keep something around? Most programs are not one line, I assure you. You can use a variable to hold a value and use it later. It's like a box that you put things in.
Let's try one out:
message = "Hello, world!"
alert message
Give that a run.
Assignment
Cool stuff! We used an = to assign the String"Hello, world!" into the
variable message. We then passed that message to the alert method.
As you can see, we can use variables in place of another value. Try this:
number = 5
number = number * 2
number = number - 8
number = number + 1
alert number
Make a guess before you run this program.
User Input
ask-ing for it.
We can ask the user of our program for some input, and then put their answer into a variable. It's easy! Check this program out:
name = ask "What is your name?"
alert "Hello, " + name
The ask method brings up a box and lets our users type something in. Fun! We
put their answer into the name variable and then showed it with alert.
Sweet!
Basic flow control
if...
Remember back to that Beginning Programming lesson... we talked about how programs are one big list, that the computer follows in order.
Well, guess what? We can actually change this order by using certain bits of code. Compare these two programs:
number = 2
if number == 2
alert "Yes!"
else
alert "No!"
end
number = 1
if number == 2
alert "Yes!"
else
alert "No!"
end
There are a few new things here.
==
Here it is again:
number = 2
if number == 2
alert "Yes!"
else
alert "No!"
end
The == command is just a bit different than the = command. == tests the Object
on its right against the Object on its left. If the two are equal, then the
code after the if will run. If they're not equal, you get the code after the
else. The end lets us know we're done with our if.
Example: a guessing game
Guess!
Let's put this all together:
secret_number = 42.to_s
guess = ask "I have a secret number. Take a guess, see if you can figure it out!"
if guess == secret_number
alert "Yes! You guessed right!"
else
alert "Sorry, you'll have to try again."
end
Can you guess what to_s does, and why you need it? If you're stumped, try
asking on the Hackety Hack site and we'll give
you a hand.
Summary
Good job!
Congrats! You've picked up all of the basics of Ruby. There's a lot more you still have to learn, though!
Here's what you've learned so far:
alert and ask
=, variables, and ==
if and else
Awesome! You'll probably want to check out Basic Shoes next!