Solidity-提款方式 - 芒果文档

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📜 Solidity-提款方式

📅 最后修改于: 2020-11-04 04:28:08 🧑 作者: Mango

提款方式可确保不会进行直接转接呼叫，这会构成安全威胁。以下合同显示不安全地使用转移电话发送以太币。

pragma solidity ^0.5.0;

contract Test {
   address payable public richest;
   uint public mostSent;

   constructor() public payable {
      richest = msg.sender;
      mostSent = msg.value;
   }
   function becomeRichest() public payable returns (bool) {
      if (msg.value > mostSent) {
         // Insecure practice
         richest.transfer(msg.value);
         richest = msg.sender;
         mostSent = msg.value;
         return true;
      } else {
         return false;
      }
   }
}

通过使最丰富的合同成为后备函数失败的合同，可以使上述合同处于无法使用的状态。当后备函数失败时，beginRichest()函数也会失败，并且合同将永远卡住。为了减轻这个问题，我们可以使用提款方式。

在提款方式中，我们将在每次转帐之前重置待处理金额。这将确保只有主叫方合同失败。

pragma solidity ^0.5.0;

contract Test {
   address public richest;
   uint public mostSent;

   mapping (address => uint) pendingWithdrawals;

   constructor() public payable {
      richest = msg.sender;
      mostSent = msg.value;
   }
   function becomeRichest() public payable returns (bool) {
      if (msg.value > mostSent) {
         pendingWithdrawals[richest] += msg.value;
         richest = msg.sender;
         mostSent = msg.value;
         return true;
      } else {
         return false;
      }
   }
   function withdraw() public {
      uint amount = pendingWithdrawals[msg.sender];
      pendingWithdrawals[msg.sender] = 0;
      msg.sender.transfer(amount);
   }
}