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How Functional Programming Made Me A Better Developer
The document discusses how learning functional programming improved the author's skills as a developer. It describes their journey learning F# by porting projects like a screenshot tool and card games. This helped them think more about pure functions, immutable data, and leveraging LINQ. It influenced how they write more testable code through interfaces and by avoiding null values. The author now considers types of components like boundaries, business rules, and workflows when building software. Overall, learning functional programming was challenging but improved their ability to design maintainable and testable systems.
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How Functional Programming Made Me A Better Developer
- 1. How Functional Programming MadeMe A Better Developer Cameron Presley @PCameronPresley http://blog.TheSoftwareMentor.com
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- 3. Little About Me ī´From Knoxville, TN ī´ Software Engineer at Pilot Flying J ī´ Musician, board gamer, and mentor ī´ Co-organizer of FunctionalKnox
- 4. Outline ī´ The Journeyof Learning Functional Programming ī´ How My Style Has Evolved ī´ How I Think About Software ī´ Resources
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- 6. Some SOLID Inspiration ī´Mnemonic for software design coined by Robert C. Martin ī´ By following SOLID, we tend to write more maintainable code ī´ Teach and present on SOLID a lot ī´ Want to focus on the Single Responsibility Principle
- 7. Some SOLID Inspiration âThesingle responsibility principle states that every module or class should have responsibility over a single part of the functionality provided by the software, and that responsibility should be entirely encapsulated by the class.â -Wikipedia
- 8. Some SOLID Interpretation Whathappens if you follow Single Responsibility to the extreme? Lots of small classes with a single method Felt like a lot of ceremony
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- 11. Seems Like IWasnât The First With This IdeaâĻ http://blog.ploeh.dk/2014/03/10/solid-the-next-step-is-functional/
- 12. Markâs Thoughts ī´ ExtremeSRP and ISP, leads to a lot of fine grain classes ī´ An object can be thought of data with behavior ī´ What if we flipped that concept around? ī´ Behavior with data ī´ Sounds like a functional approach to the problem
- 13. Time to LearnFunctional ī´ Chose F# ī´ Familiar with the .NET framework ī´ Comfortable with the .NET tooling ī´ Community resources
- 14. Steps Along TheJourney Link
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- 16. Premise ī´ Decided toport a C# application (Task Snapper) ī´ Grabs a screenshot every so often ī´ Focus on the language, not the problem ī´ Dipping my toes into FP
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- 18. Reflection ī´ Itâs F#! ī´Wrote object-oriented in a functional language ī´ Definitely not idiomatic ī´ Didnât really see the point ī´ Need to learn more about functional
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- 20. Premise ī´ Found outthat card games tend to be a great exercise ī´ Want to use Love Letter as an example card game ī´ 8 different kinds of cards, each with their own special rules ī´ Write more idiomatic functional ī´ No classes, no exceptions
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- 22. Reflection ī´ No exceptions! ī´Learning more about data modeling ī´ Making illegal state unrepresentable ī´ Game rules a bit more complicated than expected ī´ Spending a lot of time learning the problem, not solving the problem
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- 24. Premise ī´ Modeling acard game still makes sense ī´ Something with easier business rules ī´ Able to solve a real problem without getting lost ī´ Decided on Blackjack ī´ Just enough business rules to do something
- 25. Making Illegal StatesUnrepresentable
- 26. Business Rules forHow Many Points a Card Is Worth
- 27. Business Rules ForAdding Points Together
- 28. Calculating How ManyPoints For A Hand
- 29. Reflection ī´ Comfortable withhandling errors without exceptions ī´ Using pattern matching more effectively ī´ Working with built-in List operators ī´ Map and Reduce ī´ Starting to think about how to use these concepts in C#
- 30. At the End ī´Worked on/off over the course of the year ī´ Got frustrated at times ī´ Spent time learning, asking questions on Twitter, StackOverflow ī´ Didnât give up ī´ Starting to think about these concepts in OOP
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- 33. Why Write TestableCode? ī´ If code is easy to test, itâs usually easy to maintain ī´ Implies that hard to test code may not be maintainable ī´ What defines easy to test code?
- 34. A Hypothetical Pretend wewere writing tests around a particular method. Which one would you rather test? A) A method that when given the same two inputs, it returns the same output B) A method that when given the same two inputs, it returns different outputs
- 35. Thinking About Testability ī´If a method always returns output solely based on inputs, we call that method pure. ī´ No side effects or state involved ī´ Easiest types of test to write ī´ No mocking, no fake implementations to use ī´ Frameworks that use this concept ī´ Reducers (Redux) ī´ Elm architecture
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- 38. Typical Approach ī´ Whenworking with a list of data, Iâd typically work with a for each loop.
- 39. A Different Approach ī´In functional programming, typically work with multiples of data as lists ī´ Typically use built-in list functions (map, filter)
- 40. Leveraging LINQ ī´ Insteadof Map and Filter, LINQ uses Select and Where
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- 43. How I UsedInterfaces
- 44. What Is anInterface ī´ Itâs a guarantee that a method with that signature exists ī´ Essentially a contract ī´ If the contract is not fulfilled, the compiler tells you ī´ Allows us to use the compiler to find errors ī´ âLeaning on the compilerâ
- 45. Pop Quiz! Given thisinterface, what should GetById return? Anything that implements this interface will always return a Record object, right?
- 46. How about thisimplementation?
- 47. Interfaces That DonâtLie ī´ Interface says that a Record will always be returned ī´ If I handle the Record, then the compiler is happy ī´ However, the compiler canât enforce that I handled the null condition ī´ Likely for me to introduce bugs into the system
- 48. The Functional Approach ī´No concept of null, typically use something called Option or Maybe ī´ Has two values, either Some<âa> or None
- 49. The Functional Approach ī´If a function returns an Option, callers must deal with it. ī´ Otherwise, code fails to compile
- 50. How My StyleEvolved ī´ Using purity to make business rules testable ī´ Reducing complexity by leveraging LINQ ī´ Think more about types and interfaces
- 51. How I ThinkAbout Software
- 52. Types of Components ī´Boundary ī´ How data comes in or goes out of the system ī´ Business Rule ī´ How to work with data for our business needs ī´ Workflows ī´ Combines both boundary and business rule components
- 53. Boundary Components ī´ Anythingthat deals with getting data in/out of a system is a boundary ī´ Examples include databases, servers, file system, user input, etc. ī´ Makes sense to have these components implement an interface for testability ī´ Inspired by Hexagonal Architecture by Alistair Cockburn
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- 56. Business Rule Components ī´Contain the rules for our application ī´ Will make up the bulk of your application ī´ Remember SOLID principles while implementing ī´ For testability, purity is key
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- 58. Workflow Components ī´ Combinesboth Boundary and Business Rule components ī´ Can be described as ī´ Data comes in through the boundary ī´ Data is processed by the business rules ī´ Data goes out through the boundary
- 59. Bringing It AllTogether
- 60. Bringing It AllTogether
- 61. Bringing It AllTogether
- 62. Bringing It AllTogether
- 63. Wrapping Up ī´ Learningfunctional was hard for me ī´ Lots of failures, but improved incrementally ī´ Made me re-evaluate how I build software ī´ Still use functional concepts in my coding ī´ Even if Iâm not using a functional language
- 64. Resources ī´ F Sharpfor Fun and Profit (https://fsharpforfunandprofit.com) ī´ The Book of F#: Breaking Free with Managed Functional Programming by Dave Fancher ī´ F# Jumpstart (Pluralsight Course) by Kit Eason ī´ Mark Seemannâs blog: (http://blog.ploeh.dk) ī´ Hexagonal Architecture (post) by Alistair Cockburn
Editor's Notes
- #15Â I worked on/off with functional for a year Lots of heads down, then come up for air for a bit Rinse and repeat Took three attempts for me to really âgetâ it