Type Safety in an Unsafe World With Kotlin
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Cody Engel discusses type safety in Kotlin and how it helps make programming safer even when interacting with unsafe external APIs. Kotlin uses strict typing to prevent errors at compile-time. While external APIs may use unsafe patterns like nullable types, Kotlin provides features like null safety checks and extension functions to safely work with these APIs. The talk concludes by providing recommendations for designing safer APIs, such as using strict specifications and standardized formats like Protocol Buffers instead of JSON.
Type Safety in an Unsafe World With Kotlin
- 1. Type Safety in an Unsafe World with Kotlin Cody Engel, Staff Software Engineer @ PayPal
- 2. What is Type Safety? It is kind of confusing. Photo: Matthew Hamilton via Unsplash
- 3. Robin Milner, A Theory of Type Polymorphism in Programming “Well typed programs cannot go wrong.”
- 4. Going Wrong Syntactically valid, but meaningless. Type Safety by Michael Hicks - http://bit.ly/ple-type-safety
- 5. Well Typed It may crash, but that is by design in Kotlin. Type Safety by Michael Hicks - http://bit.ly/ple-type-safety
- 6. Well Typed, Continued This is by design in Ruby and may also crash. Type Safety by Michael Hicks - http://bit.ly/ple-type-safety
- 7. Cody Engel, Type Safety in an Unsafe World with Kotlin “Some languages have stricter behavior than others.”
- 8. What is Kotlin? It is a strict, yet concise programming language. Photo: Marc Reichelt via Unsplash
- 9. Define Types Name can be inferred to be a String.
- 10. Define Mutability A variable defined as “var” can change.
- 11. Define Structures Structured data is more predictable.
- 12. Define Nullability Nullability is opt-in.
- 14. And The Unsafe World? That would be our APIs. Photo: Jason Yoder via Unsplash
- 15. is_admin As a boolean it works well. Unfortunately, this wasn’t how it was actually modeled.
- 16. is_admin Our permissions class was never safer! However this is how we would model that information in Kotlin.
- 17. is_admin Okay, technically this isn’t too bad. Although, it is not the best way to model a boolean with JSON.
- 18. is_admin Extension functions to the rescue. This could also be an extension property, but extension functions look better in Keynote 😉
- 19. is_admin Strings can also represent numeric values which can represent booleans. I was pretty excited to make use of extension functions, so it was fine.
- 20. is_admin Unfortunately String already has a toBoolean function. And that function is for converting “true” and “false” into a boolean 🤦
- 21. is_admin I can’t recall if this was actually possible with the API. However there is a good chance it could have been possible based on customer configurations.
- 22. is_admin Fortunately, it isn’t too difficult to add. Nonetheless, it’d be great if this wasn’t required in the first place 😉
- 23. is_admin It was nullable though. That’s okay though, nullability is actually pretty simple with Kotlin.
- 24. is_admin Updating our extension function to be on a nullable Any works. Since we type cast on non-null types, the else branch catches our null case.
- 25. Making The World a Safer Place How to design safer APIs. Photo: Matthew Rumph via Unsplash
- 26. Stick to a strict API when rolling your own specification.
- 27. Use an industry standard specification, such as Open API.
- 28. Look at JSON alternatives such as Protocol Buffers.
- 29. Let’s build some great and safe APIs. • YouTube - bit.ly/cody-yt • Twitter - bit.ly/cody-twitter • Medium - bit.ly/cody-medium Thanks!