Solidity智能合约报错：uint256不存在length成员问题求助

核心错误定位 #

报错的直接原因是**userAccounts的类型定义错误**：
你当前定义的userAccounts是mapping(address => uint)，这意味着每个地址对应一个单一的uint值，而uint类型并没有length属性，代码中userAccounts[owners[idx]].length >= 3这一行试图访问uint的length，自然触发错误。

同时，你原本的意图是让userAccounts存储每个用户拥有的所有账户ID数组，所以类型应该定义为mapping(address => uint[])（地址到uint数组的映射）。

具体修复步骤 #

1. 修正userAccounts的类型 #

将合约中的：

mapping(address => uint) userAccounts; // store the accounts that the users own

修改为：

mapping(address => uint[]) userAccounts; // store the accounts that the users own

2. 修复WithdrawRequest结构体的amount类型错误 #

结构体中amount被错误定义为address类型，应该改为uint：

struct WithdrawRequest {
    address user; // who request the withdraw
    uint amount; // 原先是address，改为uint
    uint approvals; // check to determine if the withdraw is approved
    mapping(address => bool) ownerApproved;
    bool approved;
}

3. 修复getApprovals函数的返回值缺失 #

该函数没有返回语句，补充return：

function getApprovals(uint accountId, uint withdrawId) public view returns (uint) {
    return accounts[accountId].withdrawRequests[withdrawId].approvals;
}

4. 验证createAccount函数的逻辑正确性 #

修正userAccounts类型后，userAccounts[owners[idx]].push(id)的操作就合法了，因为现在每个地址对应的是数组，可以执行push添加账户ID。

修复后的关键代码片段 #

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.17;

contract BankAccount {
    event Deposit(
        address indexed user,
        uint indexed accountId,
        uint value,
        uint timestamp
    );
    event WithdrawRequested(
        address indexed user,
        uint indexed accountId,
        uint indexed withdrawId,
        uint amount,
        uint timestamp
    );
    event Withdraw(uint indexed withdrawId, uint timestamp);
    event AccountCreated(address[] owners, uint indexed id, uint timestamp);

    struct WithdrawRequest {
        address user;
        uint amount; // 修正类型
        uint approvals;
        mapping(address => bool) ownerApproved;
        bool approved;
    }

    struct Account {
        address[] owners;
        uint balance;
        mapping(uint => WithdrawRequest) withdrawRequests;
    }

    mapping(uint => Account) accounts;
    mapping(address => uint[]) userAccounts; // 修正为数组映射

    uint nextAccountId;
    uint nextWithdrawId;

    // 其余modifier和函数保持不变，仅上述三处修改

    function getApprovals(uint accountId, uint withdrawId) public view returns (uint) {
        return accounts[accountId].withdrawRequests[withdrawId].approvals; // 补充返回
    }
}

内容的提问来源于stack exchange，提问作者Mohamed