Smart Contract Mapping

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.2;

contract Demo {
    // 余额
    mapping(address => uint)  balances;
    // 更新
    function setBalance(uint _balance) public {
        balances[msg.sender] =  _balance;
    }
    // 读取
    function getBalance() public view  returns(uint){
        return balances[msg.sender];
    }
}