The Hidden Power of Humble Interfaces (GopherCon Singapore 2017)

Learn how to design your own interfaces in Go that are simple yet powerful – just like io.Reader and error. Discover the techniques for correctly identifying the places where interfaces will improve our code, and the specific steps to ensuring that our interfaces are as powerful as they can be.

Transcript

1. The Hidden Power of Humble
   Interfaces
   Aditya Mukerjee
   @ChimeraCoder
   GopherCon Singapore May 26, 2017
   

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2. @chimeracoder
   

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5. Why use interfaces?
   • Write less code
   • Write robust code
   • Write flexible code
   @chimeracoder
   

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6. Interfaces: The Basics
   

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7. @chimeracoder
   

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8. io.* interfaces
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9. Composite interfaces
   @chimeracoder
   

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10. Interface helper functions
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11. What makes the io interfaces powerful?
    • Abstracting a lot of common functionality
    • Lots of granularity
    • Plethora of helper functions
    @chimeracoder
    

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12. What makes error powerful?
    • Abstracts no functionality
    • Provides no granularity
    • Provides (almost) no helper functions
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13. So what makes a powerful interface, anyway?
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14. Humility and Discipline
    • Keep interfaces humble
    • Writing interfaces forces you to define the minimum required contract for
    using your types
    • Keep interfaces disciplined
    • Writing interfaces allows the compiler to enforce this contract
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15. type Foo struct interface {
    }
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16. Why Gophers avoid interfaces
    • Afraid of writing an interface that is too complicated
    • Afraid of specifying the wrong methods
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17. How I Learned To Stop Worrying and Love the interface
    • Interfaces reveal the assumptions you’re already making
    • “If it’s there, you will use it”
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18. Every time you access a field or method,
    you’re making an assumption
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19. So how should I design these interfaces?
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20. Writing interfaces like io.*
    • Don’t write helper methods until you actually find you need them
    • The contracts provided by each should be minimal
    • Create composite interface types
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21. Writing interfaces like error
    • Ask interfaces how they behave
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22. What if structs could never be exported?
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23. Aditya Mukerjee
    @chimeracoder
    https://github.com/ChimeraCoder
    Thank you!
    

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