Object#nil?

obj.nil? -> true or false

Returns: true or false · Updated March 13, 2026 · Core Classes

nil null checking conditionals

The nil? method is defined on Object and returns true if the object is nil, and false otherwise. In Ruby, nil represents the absence of a value—the only member of the NilClass. Every other object returns false when nil? is called.

Syntax

object.nil?

Parameters

nil? takes no parameters.

Examples

Basic usage

nil.nil?
# => true

"hello".nil?
# => false

42.nil?
# => false

Checking for nil in conditionals

def find_user(id)
  user = database.find_by(id: id)
  
  if user.nil?
    puts "User not found"
    return nil
  end
  
  user
end

# Before using a potentially nil value
name = params[:user]&.fetch(:name)

if name.nil?
  name = "Anonymous"
end

Common Patterns

The nil check pattern

Ruby developers frequently check for nil before using values:

def greet(user)
  return "Hello, stranger!" if user.nil?
  
  "Hello, #{user.name}!"
end

Combining with logical operators

# Use || to provide a default value
name = nil_value || "default"

# Use && for conditional execution
result = value && process(value)

Hash.fetch with default

Instead of checking nil?, use Hash#fetch:

config = { timeout: 30 }

# Instead of:
timeout = config[:timeout]
timeout = 60 if timeout.nil?

# Use:
timeout = config.fetch(:timeout, 60)

Errors

Calling nil? never raises an error—it works on all objects.