First Or Default Null (ARCH6078)

Key ruby.performance.first-or-default-null · Severity warning · Category performance

Taking the first element of a filtered collection with [0] or .first returns nil when the result is empty, and the following access raises NoMethodError. Add an emptiness guard.

Incorrect

def first_admin_name(users)
  users.select(&:admin?).first.name
end

Correct

def first_admin_name(users)
  admin = users.find(&:admin?)
  admin&.name
end

Fix

Check for nil before using the first element, or use safe navigation (&.).