Stop ignoring pattern matching!

Pattern matching was introduced as a major language feature in Ruby 2.7 and has been improved in subsequent releases, but not many people are using it yet. It’s really helpful and can make your programs clearer, simpler, safer, or all three. So why aren’t you using it? You should totally use it! I’ll show you how.

Given at Brighton Ruby 2022. A video is available at https://tomstu.art/stop-ignoring-pattern-matching.

Transcript

1. Tom Stuart, Brighton Ruby 2022 Stop ignoring pattern matching! It’s really good!
2. ! Hi, I’m Tom, I work at Shopify
3. “get the most out of Ruby”
4. Pattern matching
5. It was added to Ruby 2.7 in 2019
7. It’s really helpful and it can make your code clearer, simpler & safer It’s really helpful and it can make your code clearer, simpler & safer
8. Here is what I am about to say Not including this slide, that would take forever • Briefly: why bother? • OK OK, what’s pattern matching? • The basic bits • The intermediate bits • The advanced bits • Gotchas • The end
9. Briefly: why bother?
21. So why aren’t you using it?
22. OK OK, what’s pattern matching?
23. https://docs.ruby-lang.org/en/3.1/syntax/pattern_matching_rdoc.html “Pattern matching is a feature allowing deep matching of structured values: checking the structure and binding the matched parts to local variables.”
24. Recognising values & extracting their pieces Recognising values & extracting their pieces
25. expression in pattern # returns true or false expression => pattern # succeeds or raises as of Ruby 3.1.2
26. case expression in pattern # … in pattern # … in pattern # … end # succeeds or raises as of Ruby 3.1.2
27. A completely separate syntax A completely separate syntax
28. Patterns: the basic bits
29. Value pattern
32. Array pattern
34. Hash pattern
36. Alternative pattern
38. Smash them all together!
40. Idea: “case when” → “case in”
45. Patterns: the intermediate bits
46. Rest pattern
48. Variable pattern
52. Smash them all together!
54. Real-world examples
58. Patterns: the advanced bits Please read the documentation, it’s good actually • Guard clauses • Variable and expression pinning • Array pattern coercion (#deconstruct) • Hash pattern coercion (#deconstruct_keys) https://docs.ruby-lang.org/en/3.1/syntax/pattern_matching_rdoc.html
59. Okay, that was a lot about pattern matching
60. (Maybe this is why you’re not using it?)
61. Gotchas
62. Rails doesn’t embrace pattern matching yet
63. (Maybe this is why you’re not using it?)
70. Undefined behaviour
71. e.g. variables in unmatched patterns
74. “Experimental”…
78. “Find patterns” are still experimental in Ruby 3.1
81. …but Ruby moves on
82. In summary then
83. In summary then Big picture ideas you can remember • Ruby has pattern matching now • …and has done for years • it can make your code clearer, simpler and safer • …so it’s a huge shame to ignore it! • don’t be afraid of new Ruby features, and don’t shy away from trying stuff even if you don’t see other people doing it — someone has to go first
84. In summary then Concrete things you can actually do • try converting “case when” to “case in” to get some easy benefits • look for opportunities to match the entire shapes of arrays and hashes instead of checking their elements individually • once you’re comfortable, dip a toe into more advanced features (guards, variable pinning, #deconstruct & #deconstruct_keys, find patterns) to get more power out of pattern matching • write a conference talk or a blog post and spread the word
85. https://tomstu.art/stop-ignoring-pattern-matching Thanks!