Repeated Work In Loop (ARCH6072)

Key ruby.performance.repeated-work-in-loop · Severity warning · Category performance

A computation whose inputs do not depend on the loop variable is wasted work when rerun each iteration. Hoist the invariant expression out of the loop.

Incorrect

def filter(items, config)
  items.select do |item|
    item.score > config.thresholds.fetch(:min)
  end
end

Correct

def filter(items, config)
  min = config.thresholds.fetch(:min)
  items.select { |item| item.score > min }
end

Fix

Compute loop-invariant expressions once and assign them to a variable before the loop.