Data Types

Learning Goals

• Identify and use 4 basic Data Types
• Assign and reassign variables in Ruby
• Comfortably use irb within the Terminal

Vocabulary

• assignment operator
• Boolean
• Data Type
• Float
• Integer
• irb (interactive Ruby)
• String
• variable

Where To Run Code

By the end of this lesson, you’ll be able to use the your Terminal, specifically a tool called irb, to run and check your code. This is a great tool for a beginner, as well as a seasoned software developer, to have. irb will allow you to explore and learn Ruby and test out code you’ve written in a low-stakes environment. It is quick and easy to open up the Terminal and run your code immediately.

irb: Tips & Tricks

• Open the Terminal quickly with keyboard shortcut cmd + space to open Spotlight. Then start typing “terminal” and it should auto-fill. Press return. Note: there are other ways to open your Terminal but keyboard shortcuts are most efficient and the norm in the industry.
• Regardless of your working directory, you can type irb then press return to open up an what is referred to as an “irb session”. A prompt that looks something like irb(main):001:0> will appear; you’ll eventually type code to the right of that.
• The font size of your terminal can be increased or decreased with shortcuts cmd + + or cmd + -.
• To exit the irb session, type exit in all lowercase, then press return.

Data Types

In this lesson, we will use 4 of Ruby’s Data Types. A Data Type classifies each piece of data in a Ruby program.

• String - Any series of characters (alpha, numeric, or symbol) between quotation marks
• Integer - Any whole positive or negative number, including 0
• Float - Any positive or negative number that involves a decimal
• Boolean - true or false

To connect to how these data types are used in an application we all have some experience with, consider the steps you took to enroll at Turing in the Populi application:

• String - You provided your email address and it was stored as a string, for example: "helloworld@gmail.com"
• Integer - You provided your date of birth and the program calculated your age, for example: 37
• Float - You paid your deposit and that amount was stored as 1200.00
• Boolean - Once you paid your deposit, the “paid deposit” field said true

Variables

Pieces of data in the various types we’ve discussed so far are valid Ruby code just as they are. We can demonstrate that by typing "helloworld@gmail.com" or 37 or false into irb. We know they are valid because we don’t get an error. If helloworld@gmail.com is typed in, we will get an error, and possibly a helpful suggestion, because we didn’t include quotations around that string data!

However, if we ever want to reference that email address ever again in our code, the only way would be to read that part of the screen and manually type it out again - and that’s not going to make for a very efficient application.

Variables are what allow us to store data in a Ruby program. We can think of them as storage containers that hold items we care about and want to keep track of. The label on top of that container is what we can compare to a variable name. Variables can store any of the Data Types we’ve learned today as well as others that you’ll learn about in upcoming lessons.

Variable Syntax

In Ruby, we define variables by typing the name of the variable we wish to create, the assignment operator, then the value being stored.

email = "helloworld@gmail.com"
starting_age = 37
amount_paid = 1200.00
deposit_paid = true

To describe the first line of code in the previous example, one might say “This line of code declares a variable named email and assigns it to the String of helloworld@gmail.com”.

If our Ruby program has data stored in variables, we are able to reference those variables at any time to access the data. This can be demonstrated in irb.

Best Practices for Naming Variables

Naming can be hard, but is important to be thoughtful about and follow conventions of the language you are working with so that your code is easily accessible and readable for those you are collaborating with. A few key points:

• All Ruby variables should use snake_case - all characters should be lower cased; in multi-word variables, words should be separated with an underscore.
• Variable names should describe the type of data they hold without being overly verbose or specific (examples: name, email, etc. non-examples: x, ftga23, name_of_incoming_mod_1_back_end_student).

Reassigning Variables

We often need to write code that changes the data stored in a variable. Consider this Populi example:

• When a student first creates a profile, the deposit_paid variable is automatically assigned to false.
• Once the student pays their deposit, some code is triggered to change that value to true.

To do that, we use the exact same syntax that we used to make the original assignment.

Run the code that follows in irb to demonstrate that the value has changed.

# the deposit_paid variable is declared and assigned to the boolean value false
deposit_paid = false
# if you call the variable, the value stored in the variable (false) will be returned
deposit_paid 

# the deposit_paid variable is reassigned to the boolean value true
deposit_paid = true
# if you call deposit_paid, the new value stored in that variable will be returned (true)
deposit_paid

puts vs print

In an irb session, simply calling a variable returns the value stored in that variable and irb shows you that return value in the terminal. The value after the => symbol is the return value. However, when you start working in a ruby file, the return value does not show! It’s there, but it doesn’t visually show on the screen.

In order to visually see the return value of a variable, we can use the puts or print command before any variable or even data to see that value printed to the console.

The difference between the two is that puts will log each statment to the console on a new line, while print will log statements side by side, without any spacing in between. Take a look at this replit to see those commands in action.

Practice

Note: If at anytime you have questions, please ask them in your slack channel. This is the main resource we will use for asking questions at Turing.

1. Create a new directory called variable_practice.
2. Inside that directory, create a file called variables.rb.
3. In your variables.rb file, add a few variables that are assigned to Strings.
4. In your variables.rb file, add a few variables that are assigned to Integers.
5. In your variables.rb file, add a few variables that are assigned to Floats.
6. In your variables.rb file, add a few variables that are assigned to Booleans.
7. In your variables.rb file, leave the original String variables as declared, but add some code to reassign them to different values.
8. Write several puts statements.
9. NEW Run your code by going to the Terminal and typing ruby variables.rb - make sure you are inside the variable_practice directory when doing so. You should see the output of your ruby file in the terminal. If done correctly, where ever you have a puts or print statement, what follows should print to your terminal.

Check For Understanding

Please create a section in your Mod 0 Gist for Data Types and record your answers to these questions. (Including the question is very helpful!)

• How confident do you feel with the content on Data Types so far?
• Is there any additional learning you need or want to do before moving to the next lesson?
• What questions do you have about Data Types?