How to Check Data Type in Ruby: Simple Syntax and Examples

In Ruby, you can check the data type of any object by calling the .class method on it. This method returns the class name of the object, which represents its data type.

Syntax

Use the .class method on any Ruby object to find out its data type. The syntax is simple:

• object.class - returns the class (data type) of the object.

ruby

object.class

Example

This example shows how to check the data type of different objects like a number, a string, and an array.

ruby

number = 42
puts number.class  # Output: Integer

text = "hello"
puts text.class    # Output: String

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

Output

Integer
String
Array

Common Pitfalls

Sometimes beginners expect .class to return a simple type name like 'int' or 'str' as in other languages, but Ruby returns the full class name like Integer or String. Also, .class works on objects, not on variable names directly.

Wrong way:

value = 10
puts value.class  # Returns Integer
puts Integer.class  # This returns Class, not the type of a variable

Right way:

value = 10
puts value.class  # Returns Integer

ruby

value = 10
puts value.class  # Correct usage

Output

Integer

Quick Reference

Object	Data Type Returned by .class
42	Integer
3.14	Float
"hello"	String
[1, 2, 3]	Array
{a: 1, b: 2}	Hash
true	TrueClass
nil	NilClass

Key Takeaways

Use the .class method on any Ruby object to find its data type.

The .class method returns the object's class name, like Integer or String.

Always call .class on the object, not on the class name itself.

Common Ruby data types include Integer, String, Array, Hash, TrueClass, and NilClass.

Checking data types helps understand what kind of data you are working with.