獲取空白地址

我的程式碼有一點問題。我試圖用變數currentSenderand分別跟踪交易的目前發送者和前一個發送者lastSender，然後將它們註冊到嵌套在 struct 中的映射中Order。然而，通過我創建的 get 函式，我看到所有lastSender變數都給了我空白地址，同時currentSender給了我好的地址。

這是程式碼：

pragma solidity  ^0.5.16;

contract SupChain{
struct Status{
   address currentSender;
   address lastSender;
   string test;
   }

struct Order{
   uint256 orderID;
   uint256 NumberOfUpdate;
   string test2;
   mapping (uint256 => Status) statutes;
   }

uint256 public orderCount = 0;

mapping (uint256 => Order) public orders;


function createOrder(string memory test, string memory test2) public{
   orderCount++;
   Order storage newOrder = orders[orderCount];
   orders[orderCount] = Order(orderCount, 0, test2);
   newOrder.statutes[newOrder.NumberOfUpdate++] = Status(msg.sender, msg.sender, test);
   }

function storeOrder(uint256 id, string memory test) public{
   Order storage concernedOrder = orders[id];
   
   //Getting the previous sender before updating the NumberOfUpdate
   Status memory previousStatus = concernedOrder.statutes[concernedOrder.NumberOfUpdate];
   address previousSender = previousStatus.currentSender;
   
   concernedOrder.NumberOfUpdate = concernedOrder.NumberOfUpdate++;
   concernedOrder.statutes[concernedOrder.NumberOfUpdate++] = 
                           Status(msg.sender, previousSender, test);
   }

function getStatus(uint256 id, uint256 concernedStatusNumber) public view              
                  returns(address _currentSender, address _lastSender, 
                          string memory _test){
   Order storage concernedOrder = orders[id];
   Status memory concernedStatus = concernedOrder.statutes[concernedStatusNumber];
   return(concernedStatus.currentSender, concernedStatus.lastSender, 
          concernedStatus.test);

   }
}

所以，我想請求一些幫助來解決這個問題。

我提前感謝任何願意花時間幫助我的人。

我嘗試了什麼：

從函式中省略新訂單的遞增，createOrder並且顯然讓 else 與以前相同：

function storeOrder(uint256 id, string memory test) public{
   Order storage concernedOrder = orders[id];

   //Getting the previous sender before updating the NumberOfUpdate
   Status memory previousStatus = concernedOrder.statutes[concernedOrder.NumberOfUpdate];
   address previousSender = previousStatus.currentSender;

   concernedOrder.NumberOfUpdate = concernedOrder.NumberOfUpdate++;
   concernedOrder.statutes[concernedOrder.NumberOfUpdate] = 
                           Status(msg.sender, previousSender, test);
   }

previousStatus為函式的變數添加一個減量，storeOrder並保持與以前相同：

function storeOrder(uint256 id, string memory test) public{
   Order storage concernedOrder = orders[id];

   //Getting the previous sender before updating the NumberOfUpdate
   Status memory previousStatus = concernedOrder.statutes[concernedOrder.NumberOfUpdate--];
   address previousSender = previousStatus.currentSender;

   concernedOrder.NumberOfUpdate = concernedOrder.NumberOfUpdate++;
   concernedOrder.statutes[concernedOrder.NumberOfUpdate++] = 
                           Status(msg.sender, previousSender, test);
   }

現在我正在查看問題是否來自我的getStatus功能

您變空的原因是因為您在創建訂單時lastSender正在遞增。newOrder.NumberOfUpdate++它將狀態儲存在索引處0並遞增變數。當您設置訂單時，它會檢索增加的值，該值1在該點上並且沒有針對該索引的狀態，因為狀態儲存在 index0中。

您可以省略 in 的遞增，createOrder也可以 在檢索舊狀態時NumberOfUpdate遞減in 。1``setOrder

您的 createOrder 令人困惑，請嘗試這樣

function createOrder(string memory test, string memory test2) public{
   orderCount++;
   orders[orderCount] = Order(orderCount, 0, test2);
   orders[orderCount].NumberOfUpdate++;
   orders[orderCount].statutes[orders[orderCount].NumberOfUpdate] = Status(msg.sender, msg.sender, test);
}

我建議不要從 1 開始您的訂單計數，作為開發人員處理沒有 0 索引的數組/映射會令人困惑。從我的角度來看，這樣的東西看起來更好。

function createOrder(string memory test, string memory test2) public{
   // orderCount  is 0 for first order
   orders[orderCount] = Order(orderCount, 0, test2); 

   // first update update is stored at 0
   orders[orderCount].statutes[orders[orderCount].NumberOfUpdate] = Status(msg.sender, msg.sender, test);

   orders[orderCount].NumberOfUpdate++;
   orderCount++;
}

引用自：https://ethereum.stackexchange.com/questions/86934