Off the Rails: Validating non-model classes with…ActiveModel?
summary
Builds a single validator class that accepts Hash/Struct/Data and runs ActiveModel validations (built‑in and custom), using TDD and by reading validators plus ActiveSupport callbacks so options like if and allow_blank behave correctly. Handles presence, confirmation, arrays, shoulda‑matchers quirks, and a mutating‑hash bug fixed by swapping delegator for method_missing. The implementation lives in a repo as a gem scaffold with commit checkpoints and has run in production for over a year.
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chapters (20)
- 0:00Introduction
- 1:48Rails validators outside models
- 6:20Goals for flexible validator
- 7:03Proof of concept: presence validator
- 10:54Fixing initial POC errors
- 12:21Rails validator options like allow_nil
- 14:05Delegating validation methods
- 15:07Conditional validations with if/unless
- 16:09Hash keys to method calls
- 17:29Additional Rails validators
- 18:11Clearing validators and state
- 19:58Nested data and custom validators
- 21:23Class-level validate method
- 22:27Confirmation validator quirks
- 23:10Shoulda Matchers integration
- 24:14Q&A: Hash mutation and use cases
- 26:00Q&A: Real-world validation scenarios
- 27:02Q&A: Event sourcing and validation
- 28:46Q&A: Storing registered validations
- 30:08Closing
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