Steps

Step 1

Type this in the terminal to start the Interactive Ruby Shell, a program which lets you try out Ruby code:

Terminal

irb

Yours might look different, but it should look something like this:

IRB

irb(main):001:0> 

Step 2

Next try some simple math that's built into Ruby. Type these lines into IRB:

IRB

3 + 3
7 * 6

Step 3

Variables are names with values assigned to them.

IRB

my_variable = 5

This assigns the value 5 to the name my_variable.

Step 4

You can also do math with variables:

IRB

my_variable + 2
my_variable * 3

Step 5

Variables can also hold more than one value. This is called an array.

IRB

fruits = ["kiwi", "strawberry", "plum"]

Here we're using the variable fruits to hold a collection of fruit names.

Step 6

IRB

fruits = fruits + ["orange"]
fruits = fruits - ["kiwi"]

+ and - are called operators. We can use them with the array of fruits just like we can use them with numbers.

Step 7

Everything in Ruby has a class. Type this into IRB:

IRB

7.class
"kiwi".class
fruits.class

These are the three data types introduced so far: Fixnum (numbers), String (text), and Array (lists).

Step 8

Each class has different methods that can be used on instances of that class. If you're not quite sure what an instance is, this page on Ruby classes might help

IRB

fruits.length
fruits.first

You can see all the methods available for an object:

IRB

fruits.methods

And you can call multiple methods in a row:

IRB

fruits.methods.sort

In fruit.methods.sort above, fruit.methods returns an array, and .sort sorts that array. It's exactly like this, but without the array variable:

IRB

array = fruits.methods
array.sort

Step 9

Arrays have a method called each which iterates through the list running code on each item.

IRB

fruits.each do |fruit|
  puts fruit
end

This takes the first item from the fruits array ("strawberry"), assigns it to the variable fruit, and runs the code between do and end. Then it does the same thing for each other item in the list. The code above should print a list of the fruits.

Step 10

A conditional runs code only when a statement evaluates to true.

IRB

if my_variable > 1
  puts "YAY!"
end

This prints YAY! if the value stored in my_variable is greater than 1.

Try changing the > in the conditional to a <.

Step 11

You can also make your own methods:

IRB

def pluralize(word)
  word + "s"
end
pluralize("kiwi")

Methods take parameters, which are the variables they work on. In this case, we made a method called pluralize that takes one parameter, a word.

Methods can also return data. In this case, pluralize returns the word with an 's' added to the end of it. In Ruby, methods return whatever the last line of the method evaluates to.

Step 12

This is an optional practice question if you want to brush up on your Ruby. Feel free to skip it! Or talk to your TA if you get stuck, or discuss your solution once you have completed the checkpoint.

Write some Ruby that prints out the names of the people in your group.

Hints:

1. Start by opening up irb.
2. Create the names as strings in an array.
3. Store that array to a variable.
4. Then use the .each method on the stored array to loop through each of the names.
5. Use the puts method to print out the names.