Ruby NoMethodError: undefined method for nil

NoMethodError: undefined method 'name' for nil means Ruby called the method name on an object that was nil. The method exists on the object you expected, but the variable held nil, usually because a lookup found nothing. Find where the value came from (the backtrace points at the line), then handle the missing case with fetch, a guard, or the safe navigation operator &..

Message formats by Ruby version

Ruby 3.4 changed the opening backtick to a single quote in error messages. Searching for undefined method plus for nil matches every version.

Example

users = { 1 => { name: "Ada" } }
user = users[2]          # missing key: nil
puts user[:name].upcase  # undefined method '[]' for nil

The method in the message is the one called on nil: here [], because user[:name] calls user.[](:name).

Fixes

# 1. Fail loudly with a useful error when the key must exist
user = users.fetch(2)                    # KeyError: key not found: 2

# 2. Default value
user = users.fetch(2, { name: "guest" })

# 3. nil is acceptable: safe navigation returns nil instead of raising
puts user&.dig(:name)&.upcase

# 4. Guard clause
return unless user