Spotting Pure Functions in I/O Driven Code
summary
Claim: separating pure logic from IO makes code testable, refactorable and removes subtle bugs. Refactor of a food-ordering service in Scala pulls current time out as an explicit argument, finds a pure hours.encloses function, caches dayOfWeek to avoid rare clock-rollover bugs, and moves DB calls into an IO wrapper with run, map and flatMap used via for-comprehensions. Result: pure validators become trivially table-tested and facades return composable effect descriptions while actual IO runs only at the endpoint.
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chapters (9)
- 0:00Welcome and introduction
- 1:55From OOP to functional programming
- 7:37Pure functions vs IO
- 12:38Refactoring spaghetti code
- 18:01Composing pure functions
- 22:17Separating IO and logic
- 24:50Introducing IO wrapper
- 33:37Summary and conclusions
- 38:19Q&A and closing
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