ruby-on-rails - 堆栈级别太深，即使递归调用在函数末尾？

Question

我正在遵循答案 here 的建议，并确认 :tailcall_optimization=>true 和 :trace_instruction=>false，但我仍然得到:

SystemStackError: stack level too deep

...

... 8696 levels...

我做错了什么？

  def persist_shipments_then_next(prev_data)
    persist_shipments(prev_data)

    next_token = prev_data['NextToken']
    puts next_token
    unless next_token.nil?
      next_data = @client.list_inbound_shipments_by_next_token(
        next_token
      ).parse

      persist_shipments_then_next(next_data)
    end
  end

更新:我从 application.rb 中删除了以下内容，它有效吗？:

RubyVM::InstructionSequence.compile_option = {
  tailcall_optimization: true,
  trace_instruction: false
}

Answer 1

您需要为递归函数调用设置某种终止条件。您已将该条件设为 unless next_token.nil?，但您确定 next_token 在您尝试终止时变为 nil，可能您只需要执行 除非 next_token

def persist_shipments_then_next(prev_data)
  persist_shipments(prev_data)

  next_token = prev_data['NextToken']
  unless next_token
    next_data = @client.list_inbound_shipments_by_next_token(
      next_token
    ).parse

    persist_shipments_then_next(next_data)
  end
end