Class.new is all you need

RubyKaigi 2026 LT

1. RubyKaigi 2026 LT Shia@STORES Class.new is all you need
2. SIM SANGYONG (@shia) - STORES Inc. - GitHub: @riseshia - X: @riseshia Self Introduction 2
3. SIM SANGYONG (@shia) - STORES Inc. - GitHub: @riseshia - X: @riseshia - And…Day 3!!! Self Introduction 3
4. "type-guessr" needed to collect info from project code at startup and it was slow. So, I profiled and… Background 4
5. ko1: "Class.new is faster than them" shia: "…!?!?" Background 5
6. Target: Initialization speed - Data.define, Struct, Class - kwargs, positional args - 1 ivar, 8 ivars Ruby 4.0.1 / linux / no YJIT So, benchmark it 6
7. Result 7 1 field 8 fields
8. - Class.new > Struct.new >> Data.define.new - kwargs are slow - more ivars, more slower Observation 8
9. Observation 9 8 fields - Class.new > Struct.new >> Data.define.new - kwargs are slow - more ivars, more slower Note: Class.new outperforms with YJIT
10. See perf results 10 "perf record -g --call-graph dwarf" Ruby 4.0.1 / linux / no YJIT / ivar 1 field
11. See perf results 11
12. See perf results 12
13. See perf results 13
14. See perf results 14
15. See perf results 15
16. - Is kwargs initialization optimized? - Create Hash for kwargs on initialization or not - Is ivar access optimized? - Byte code caching with object shape applied or not - Does the object need to be frozen? Why?? 16
17. shia: "I found it really is.." ko1: "We optimize what people use most, so yeah" shia: "That's absolutely true😂" After talk 17
18. I originally used Data because I vaguely assumed Data/Struct was lighter than Class. Reality was different at least object initialization. Did you know that? Summary 18
19. 〜Fin〜 19
20. 🤔 20
21. If "Class" is the fastest, why not re-implement these with it?? 🤔🤔🤔 How to speed up Struct or Data.define 21
22. Re-impl Struct with "Class", and benchmark again: (8 fields, YJIT off/on) How to speed up Struct or Data.define 22
23. It’s really fast! Let’s submit this patch!!!
24. Let’s submit this patch!!! 24
25. Submit this patch…? 25
26. 🫠 26
27. 🚮 27
28. 28 You can check the full benchmark & RubyStruct implementation! https://github.com/riseshia/class-new-is-all-you-need Class.new might be all you need (if initialization perf matters)