When is it better to use a Struct rather than a Hash in Ruby?

Question

A Ruby Struct allows an instance to be generated with a set of accessors:

# Create a structure named by its constant
Customer = Struct.new(:name, :address)     #         


        

Answer 1

I have rerun @mpospelov's benchmarks on Ruby 3.0.0p0 (2020-12-25 revision 95aff21468) [x86_64-darwin20].

Simple

Warming up --------------------------------------
                hash     1.008M i/100ms
              struct   423.906k i/100ms
             ostruct    16.384k i/100ms
Calculating -------------------------------------
                hash      9.923M (± 1.9%) i/s -     50.412M in   5.082029s
              struct      4.327M (± 2.6%) i/s -     22.043M in   5.097358s
             ostruct    158.771k (± 6.7%) i/s -    802.816k in   5.084066s

Comparison:
                hash:  9923144.6 i/s
              struct:  4327316.1 i/s - 2.29x  (± 0.00) slower
             ostruct:   158771.4 i/s - 62.50x  (± 0.00) slower

Huge List

Warming up --------------------------------------
                hash    71.378k i/100ms
              struct    99.245k i/100ms
             ostruct   855.000  i/100ms
Calculating -------------------------------------
                hash    712.113k (± 4.9%) i/s -      3.569M in   5.024094s
              struct      1.098M (± 2.9%) i/s -      5.558M in   5.066160s
             ostruct      8.629k (± 4.8%) i/s -     43.605k in   5.066147s

Comparison:
              struct:  1098071.6 i/s
                hash:   712112.5 i/s - 1.54x  (± 0.00) slower
             ostruct:     8628.8 i/s - 127.26x  (± 0.00) slower

Conclusion

• If performance does matter, use struct.
• If defining fields on the fly matters, go with open struct.