Ruby Data Types

Data types classify the kind of data you're working with, such as text, numbers, and true/false values. For example,

num = 24

Here, 24 (an integer) is assigned to the num variable. So the data type of num is Integer.

Notice that we haven't explicitly specified the data type of the variable. That's because Ruby automatically infers the data type of the variable. This is known as dynamic typing.

Ruby Data Types

Some common data types in Ruby are listed in the table below:

Ruby Numbers (Integer and Float)

An integer is a number without a decimal point.

Meanwhile, a float is a number with a decimal point.

For example,

# Create and print an integer variable
marks = 85
puts marks

# Create and print a float variable
price = 99.99
puts price

Output

85
99.99

Here,

• marks is an integer variable whose value is 85.
• price is a float variable whose value is 99.99.

To learn more, visit our tutorial on Ruby Numbers.

# Display the sum of 9 and 3
puts 9 + 3

# Display the product of 2.5 and 6.9
puts 2.5 * 6.9

12
17.25

puts 9 / 4

# Output: 2

# Divide 9.0 (float) by 4 (integer)
puts 9.0 / 4
# Output: 2.25

# Divide 9 (integer) by 4.0 (float)
puts 9 / 4.0
# Output: 2.25

# Divide 9.0 by 4.0
puts 9.0 / 4.0
# Output: 2.25

Ruby String

A string is a piece of text written inside quotes. For example,

message = "Hello, I'm 29 years old."
puts message

age = '29'
puts age

Output

Hello, I'm 29 years old.
29

Here, message and age are string variables because they store a sequence of characters enclosed within quotation marks.

Note: You can use both single and double quotes to denote a string. However, we recommend you use double quotes.

To learn more, visit our tutorial on Ruby Strings.

Strings vs. Numbers

Notice that in the previous program, the age variable is storing the string '29'. Even though we understand this to be a number, Ruby interprets it as a string because the value has quotations around it.

# String value because of single quotes 
age_string = '29'
puts age_string

# String value because of single quotes
price_string = "99.99"
puts price_string

# Integer value (no quotations present)
age_int = 29
puts age_int

# Float value (no quotations present)
price_float = 99.99
puts price_float

Output

29
99.99
29
99.99

Here,

• '29' and "99.99" are strings because they have single and double quotes enclosing the number values.
• 29 and 99.99 are numbers because they are not enclosed by quotation marks.

Note: The puts method prints strings without displaying the quotation marks. Thus, the output of both puts '29' and puts 29 will be 29.

Ruby Boolean

Boolean values can be either true or false. For example,

# Print boolean values
puts true
puts false

# Create boolean variables
can_vote = true
can_drink = false

# Print the boolean variables
puts can_vote
puts can_drink

Output

true
false
true
false

Note: Booleans are used in conditional statements and loops (which we will learn in later chapters).

To learn more, visit Ruby Boolean.

Ruby Array

Arrays are a list of values. For example,

array_int = [1, 2, 3]
puts array_int

Output

1
2
3

Here, array_int is an array that consists of three integer values: 1, 2, and 3.

You can create arrays of other types as well. You can also mix data of different types into a single array. For example,

# An array of floats
array_float = [1.1, 2.2, 3.3]
p array_float

# An array of strings
array_string = ["Black Sabbath", "Deep Purple", "Led Zeppelin"]
p array_string

# Mixed array
array_mixed = ["Ash Ketchum", 10, false]
p array_mixed

Output

[1.1, 2.2, 3.3]
["Black Sabbath", "Deep Purple", "Led Zeppelin"]
["Ash Ketchum", 10, false]

Tip: Use p instead of puts when printing arrays or other complex data structures. It shows the full structure (including quotes, brackets, etc.).

To learn more, visit our tutorial on Ruby Arrays.

rock_bands = ["Black Sabbath", "Deep Purple", "Led Zeppelin"]

# Display the first element
puts rock_bands[0]

# Display the second element
puts rock_bands[1]

# Display the third element
puts rock_bands[2]

Black Sabbath
Deep Purple
Led Zeppelin

rock_bands[index]

Ruby Hash

A hash stores pairs of keys and values. It is similar to the dictionary type in other programming languages. For example,

# Create a hash named 'student'
student = {
  "id" => 121,
  "name" => "Ash Ketchum",
  "age" => 10
}

# Print the value stored in key "id"
puts student["id"]

# Print the value stored in key "name"
puts student["name"]

# Print the value stored in key "age"
puts student["age"]

Output

121
Ash Ketchum
10

Here, student is a hash that stores the following key-value pairs:

Notice that:

• Values are assigned to keys using the => symbol.
• We access values by specifying the key. For instance, student["id"] gives the value of the "id" key (121) that's stored the student hash.

To learn more, visit Ruby Hashes.

Ruby nil

The nil value in Ruby means "nothing." It's Ruby's way of saying "no value here."

name = nil
puts name

This program doesn't print anything, because nil means the variable has no value.

Ruby Symbol

A symbol is a lightweight, immutable label in Ruby. It's often used in situations where you don't need the features of a full string, such as keys in hashes.

Symbols start with a colon (:). For example,

my_symbol = :hello
puts my_symbol

# Output: hello

Here, my_symbol is a variable that stores the symbol :hello.

Notice that the puts method doesn't display the colon when printing the symbol.

student = {
  id: 121,
  name: "Ash Ketchum",
  age: 10
}

puts student[:id]
puts student[:name]
puts student[:age]

121
Ash Ketchum
10

student = {
  id: 121,
  name: "Ash Ketchum",
  age: 10
}

puts student[:id]
puts student[:name]
puts student[:age]

student = {
  :id => 121,
  :name => "Ash Ketchum",
  :age => 10
}

puts "hello".class
# Output: String

puts :hello.class
# Output: Symbol

puts 123.class
# Output: Integer

puts 12.3.class
# Output: Float

puts true.class
# Output: TrueClass

puts false.class
# Output: FalseClass

puts nil.class
# Output: NilClass

my_array = [1, 2, 3]
puts my_array.class
# Output: Array

my_hash = { name: "Ragnar Lothbrok" }
puts my_hash.class
# Output: Hash

require 'complex'
puts Complex(2, 3) # Output: 2+3i

puts Rational(1, 2) # Output: 1/2