堆栈级别太深，即使递归调用是在函数结束？

Question

我遵循答案here的建议，并确认：tailcall_optimization =＆gt; true和：trace_instruction =＆gt; false，但我仍然得到：

  

SystemStackError：堆栈级别太深

     

...

     

...... 8696级...

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中删除了以下内容并且它有效吗？

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?，但是当您尝试终止时，您确定next_token变为零，可能只需要unless 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