ruby 37 lines · 7 steps

Building an audit trail with Rails callbacks

An after_save callback records what changed on every Product write, filtering sensitive values along the way.

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Rails Intermediate callbacks audit-logging dirty-tracking data-sanitization
1class Product < ApplicationRecord
2 belongs_to :account
3 
4 after_save :record_audit_trail
5 
6 private
7 
8 def record_audit_trail
9 changes = saved_changes.except("created_at", "updated_at")
10 return if changes.empty?
11 
12 action = saved_change_to_id? ? :create : :update
13 
14 audit_logs.create!(
15 account: account,
16 actor: Current.user,
17 action: action,
18 changed_attributes: normalize(changes)
19 )
20 end
21 
22 def normalize(changes)
23 changes.transform_values do |(from, to)|
24 { from: sanitize(from), to: sanitize(to) }
25 end
26 end
27 
28 def sanitize(value)
29 return "[FILTERED]" if value.present? && self.class.filter_attributes.include?(value)
30 
31 value
32 end
33 
34 def audit_logs
35 AuditLog.where(auditable: self)
36 end
37end
01 / 01
STEP 01

Walkthrough

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Three takeaways
  1. 1Rails' dirty-tracking methods like saved_changes let you record exactly what a write changed without extra queries.
  2. 2Distinguishing create from update via saved_change_to_id? avoids passing an explicit flag through the callback.
  3. 3Sanitizing sensitive values before persisting keeps audit logs useful without leaking secrets.

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