内容简介

使用 solidity 实现的基于 ERC20 代币协议的借贷款去中心化应用平台(极简版)。实现存款、取款、贷款、还款以及利息计算的功能。

设计逻辑

• 平台提供ERC20协议代币的相关存取和利息计算工作。部署智能合约时初始化贷款和存款的年利率、代币实现地址。
• 用户可以将手中的代币存入平台，等到一定的期限再次拿出获得本金加利息。也可以向平台申请代币，在一定的期限之后自主还款即可。

ERC20TokenLoanPlatform 合约

事件

合约包含4个事件，包括 Deposit 存款、Withdrawal 取款、CreateLoan 贷款、PayLoan 还款。

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;import "erc-token-standard/ERC/IERC20.sol"; // 基于ERC20代币协议的借贷款平台 
contract ERC20TokenLoanPlatform {event Deposit(address depositor, uint amount ,uint DepositTime); event Withdrawal(address payee, uint amount, uint WithdrawalTime); event CreateLoan(address loanAddress, uint amount, uint interest, uint CreateLoanTime); event PayLoan(address loanAddress, uint amount, bool total, uint PayLoanTime); 

结构体

合约包含2个结构体， 包括 Client 客户信息、Loan 贷款信息。

	// 客户信息 struct Client {uint amount;uint depositTime; uint withdrawalTime;}// 贷款信息struct Loan {address loanAddress; uint amount;uint interest; }

状态变量

本合约使用了6个状态变量，其中有 clients 客户信息映射、loans 贷款信息映射、annualInterestRate 贷款年利率、annualDepositRate 存款年利率、tokenAddress 代币实现地址、erc20Token 代币对象。

	mapping(address => Client) private clients; mapping (uint => Loan) private loans;uint public annualInterestRate;        // 贷款年利率,如5%uint public annualDepositRate;         // 存款年利率,如2%address public tokenAddress;           // ERC20代币地址 IERC20 erc20Token; 

函数

本合约包含了8个基本函数，其中包括构造函数、deposit 存款、withdrawal 取款、createLoan 贷款、payLoan 还款、loanInquiry 待还款查询、depositInquiry 账户余额查询、balanceInquiry 客户信息查询 。

	// 构造函数constructor(address _tokenAddress, uint _initLoanInterest, uint _initDepositInterest) {tokenAddress = _tokenAddress;           // 初始化代币地址 erc20Token = IERC20(tokenAddress);      // 声明IERC20接口合约变量annualInterestRate = _initLoanInterest; annualDepositRate = _initDepositInterest;   }// 存款 function deposit(uint _amount) public {require(_amount > 0, "Amount is less than or equal to 0.");      // 存款代币数不能为0     require(erc20Token.balanceOf(msg.sender) >= _amount, "Number of tokens is insufficient.");            // 检查持有代币数是否大于等于存款代币数require(erc20Token.allowances(msg.sender, address(this)) >= _amount, "Not enough approvals.");        // 检查是否有足够的授权 erc20Token.transferFrom(msg.sender, address(this), _amount);             clients[msg.sender].amount += _amount;                      // 增加存款if (clients[msg.sender].depositTime == 0){clients[msg.sender].depositTime = block.timestamp;      // 当前的存款时间 }emit Deposit(msg.sender,_amount ,block.timestamp); }// 取款 function withdrawal(uint _amount) public {require(_amount > 0, "Amount is less than or equal to 0.");               // 取款代币数不能为0  uint timestamp = block.timestamp;   depositInquiry();                 // 计算本金 + 利息2% require(clients[msg.sender].amount >= _amount, "Insufficient balance.");         // 检查存款代币数是否大于等于取款代币数 require(erc20Token.balanceOf(address(this)) >= _amount, "Platform bankruptcy."); // 检查平台的代币数是否满足取款 erc20Token.transfer(msg.sender, _amount);            clients[msg.sender].amount -= _amount; clients[msg.sender].withdrawalTime = timestamp; emit Withdrawal(msg.sender, _amount, timestamp);}// 贷款function createLoan(uint _amount) public returns (uint){require(_amount > 0, "Amount is less than or equal to 0.");            // 贷款不能小于0        require(erc20Token.balanceOf(address(this))*10/100 >= _amount, "Exceeding the platform loan limit.");        // 超过平台总存款的10%require(erc20Token.balanceOf(msg.sender) + clients[msg.sender].amount >= _amount*20/100, "Invalid loan.");   // 账户资产数需有贷款的20%erc20Token.transfer(msg.sender, _amount); uint timestamp = block.timestamp;           // 以当前块的时间戳为贷款id值 uint interest = _amount * annualInterestRate / 100;     // 计算利率 loans[timestamp].loanAddress = msg.sender; loans[timestamp].amount = _amount; loans[timestamp].interest = interest;     // 计算利率 emit CreateLoan(msg.sender, _amount, interest, timestamp);return timestamp; }// 还款function payLoan(uint _amount, uint _loanId) public {require(_amount > 0, "Amount is less than or equal to 0.");        // 还款需大于0require(erc20Token.balanceOf(msg.sender) >= _amount, "Number of tokens is insufficient.");            // 检查持有代币数是否大于等于存款代币数require(erc20Token.allowances(msg.sender, address(this)) >= _amount, "Not enough approvals.");        // 检查是否有足够的授权 uint total = loanInquiry(_loanId);        // 计算代还款 bool fullPayment = false; // 还一部分或一次性还 if (total <= _amount) {     erc20Token.transferFrom(msg.sender, address(this), total);       // 一次性还完delete loans[_loanId];                                           // 删除贷款记录  fullPayment = true; } else {    erc20Token.transferFrom(msg.sender, address(this), _amount);        // 还了一部分 _amount loans[_loanId].amount -= _amount;                                   // 重写贷款记录 }emit PayLoan(msg.sender, _amount, fullPayment, block.timestamp);}// 待还款查询function loanInquiry(uint _loanId) public returns (uint) {require(loans[_loanId].amount != 0, "Invalid loan id.");require(loans[_loanId].loanAddress == msg.sender, "Non-personal enquiry.");// 计算需要还款的代币数: 本金 + 利息uint timestamp = block.timestamp; uint diffDays = ( timestamp - _loanId) / 86400;                 // 时间戳转换为天数 uint total = loans[_loanId].amount + loans[_loanId].interest*diffDays/365;      // 总计还款数 loans[_loanId].amount = total;            //重写用户贷款数 return total; }// 余额+利息的计算function depositInquiry() public  returns (uint){uint principal = clients[msg.sender].amount;    // 本金uint diffDays = (block.timestamp - clients[msg.sender].depositTime) / 86400;                 // 时间戳转换为天数 uint interest = principal * annualDepositRate / 100 * diffDays / 365;uint total = principal + interest;clients[msg.sender].amount = total;return total;}// 客户信息查询 function balanceInquiry() public returns (address, uint, uint, uint){depositInquiry();                 // 计算本金 + 利息2% uint balance = clients[msg.sender].amount;uint depositTime = clients[msg.sender].depositTime;uint withdrawalTime = clients[msg.sender].withdrawalTime;return (msg.sender, balance, depositTime, withdrawalTime);}
}

Remix 运行实现

部署相关智能合约

solidity实现ERC20代币标准。
先部署 ERC20 代币合约，初始化代币合约信息。

部署 ERC20TokenLoanPlatform 合约，初始化代币实现地址、贷款年利率5和存款年利率2。

首先需要给自己的账户铸造 200 个代币用于功能测试，

再给 ERC20TokenLoanPlatform 合约地址铸造一定数量的代币和授权代币转账权限，保证平台功能的正常运行。

存款和取款

调用 deposit 函数存款 100 个代币，

balanceInquiry 函数查看余额变化，这里已经显示自己的余额为刚才存入的100。

调用 withdrawal 函数取出指定数量的代币，不能超出自己的余额。平台会自动进行存款利息计算。

balanceInquiry 函数查看余额变化，这里已经显示自己的余额还剩下50。

贷款和还款

调用 createLoan 函数输入自己需要贷多少代币。在这里注意账户的资产需要有贷款数的20%才有资格贷款。成功后拿到此次贷款的id值 1703236890。

调用 payLoan 函数输入贷款的 id 值进行还款，可以先还一部分也可以一次性还完，平台会自动进行贷款利息计算。

调用 loanInquiry 函数输入贷款的 id 值进行待还款的查询。

源码地址

本文只是简单介绍，具体实现看代码。gitee 开源地址。

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