即使遞歸調用在函數結束時堆棧級別太深？

Question

我下面的答案here的建議，並已證實：tailcall_optimization =>真實：trace_instruction =>假的，但我仍然得到：

SystemStackError: stack level too deep

...

... 8696 levels...

我在做什麼錯？

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：我刪除從application.rb中以下和它的作品WTF？：

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

Answer 1

你需要有某種形式的遞歸函數調用結束條件。你已經把該條件爲unless next_token.nil?，但你肯定next_token成爲當你試圖終止零，可能是你需要做的僅僅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