til/ruby/open-struct-has-bad-performance-characteristics.md

OpenStruct Has Bad Performance Characteristics

The Ruby docs for OpenStruct have a Caveats section that warns about the poor performance characteristics of OpenStruct relative to Struct and Hash.

This should be a consideration if there is a concern about the performance of the objects that are created, as there is much more overhead in the setting of these properties compared to using a Hash or a Struct. Creating an open struct from a small Hash and accessing a few of the entries can be 200 times slower than accessing the hash directly.

This doesn't mean don't use OpenStruct, but do be aware of if you are using it in a hot path or if you are allocating and processing tons of them.

If you turn on Performance Warnings in Ruby, you'll see a warning message when allocating an OpenStruct.

> require 'ostruct'
=> true
> os1 = OpenStruct.new
=> #<OpenStruct>
> Warning[:performance] = true
=> true
> os2 = OpenStruct.new
(irb):6: warning: OpenStruct use is discouraged for performance reasons
=> #<OpenStruct>

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