Index your State for Safer Functional APIs
summary
Claims that using IndexedState in Scala (via Scalaz/StateT) enforces API call order at compile time rather than relying on runtime checks. Demonstrates transforming a mutable-style connection/cache API into an immutable, indexed-state API that threads a cache through Future-based effects and rejects invalid call sequences (e.g., update before lock) by failing to compile. Shows types, flatMap mechanics, contravariance benefits, and a small transactional cache/lock/update/commit example that works under the indexed-state model.
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chapters (7)
- 0:00Identifying API flaws
- 1:47Immutable API design
- 3:22Basics of the state monad
- 7:34State transformers
- 10:46Introduction to indexed state
- 13:34Enforcing state transitions
- 16:54Trade-offs and conclusion
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