module_prepend_for_instrumentation

🔍 Instrumentation via Module#prepend

Use Module#prepend to inject behavior before or after target methods without altering the original class. This approach ensures your instrumentation runs in the proper ancestor chain and can call super to delegate to the original implementation.

module MethodProfiler
  def self.prepended(base)
    base.instance_methods(false).each { |m| wrap_method(base, m) }
  end

  def self.wrap_method(base, method)
    base.define_method(method) do |*args, &blk|
      start = Process.clock_gettime(Process::CLOCK_MONOTONIC)
      result = super(*args, &blk)
      duration = Process.clock_gettime(Process::CLOCK_MONOTONIC) - start
      puts "#{method} took #{duration.round(4)}s"
      result
    end
  end
end

class DataFetcher
  def fetch; sleep(0.1); 'data'; end
  prepend MethodProfiler
end

DataFetcher.new.fetch  # Outputs: "fetch took 0.1001s"