Bringing Swift enums to Objective-C with macros

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In Objective-C you can achieve similar clear and correct expressive power if you sacrifice concision, with a mixture of inheritance and blocks, or by using the visitor pattern. Due to the massive amount of boilerplate you need, you don't reach for these patterns nearly as often as you should. However, you have a tool to manage boilerplate in Objective-C -- preprocessor macros! Despite the limitations of the macro substitution system, with a few macro tricks, you can build a massive macro that can give us algebraic data types with none of the boilerplate. You can declare our types just as you would with Swift enums!

ONE_OF(PIBarCode,

CASE(QrCode, NSString *, code),

CASE(Upc, NSNumber *, num1, NSNumber *, num2, NSNumber *, num3, NSNumber *, num4)

)

In this talk, Brandon will cover why algebraic data types matter, how it's possible to represent them in Objective-C (albeit verbosely), how you can remove the verbosity with macros, and the downsides and upsides of using this one-of macro.

Brandon is passionate about finding and sharing ways to write clean, maintainable code, increasing our industry's productivity. Features of modern programming languages, like Swift's enum, helps you to write correct code on the first try -- functional programming can get us there.

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