Pre:

DoDo支持flash loan,并且手续费上比较友好

注：DODO V2 闪电贷仅当返还的base quote 数量比例产生变化时，合约会预览一笔将base quote 磨平的交易，该磨平交易手续费作为闪电贷手续费。其他情况不收取手续费用

试试在rinkby测试网上能否执行借款还款操作

DoDo闪电交换机制:

Code:

solidity代码:

参考文档里闪电交换，有代码例子该代码则是只实现了借款和还款的操作，具体的借款后的操作逻辑还要自己实现

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "./interface/IDODO.sol";
import "./interface/Withdraw.sol";

contract Flashloan is Withdraw{

    function dodoFlashLoan(
        address flashLoanPool, //You will make a flashloan from this DODOV2 pool
        uint256 loanAmount, 
        address loanToken
    ) external  {
        //Note: The data can be structured with any variables required by your logic. The following code is just an example
        bytes memory data = abi.encode(flashLoanPool, loanToken, loanAmount);
        address flashLoanBase = IDODO(flashLoanPool)._BASE_TOKEN_();
        if(flashLoanBase == loanToken) {
            IDODO(flashLoanPool).flashLoan(loanAmount, 0, address(this), data);
        } else {
            IDODO(flashLoanPool).flashLoan(0, loanAmount, address(this), data);
        }
    }

    //Note: CallBack function executed by DODOV2(DVM) flashLoan pool
    function DVMFlashLoanCall(address sender, uint256 baseAmount, uint256 quoteAmount,bytes calldata data) external {
        _flashLoanCallBack(sender,baseAmount,quoteAmount,data);
    }

    //Note: CallBack function executed by DODOV2(DPP) flashLoan pool
    function DPPFlashLoanCall(address sender, uint256 baseAmount, uint256 quoteAmount, bytes calldata data) external {
        _flashLoanCallBack(sender,baseAmount,quoteAmount,data);
    }

    //Note: CallBack function executed by DODOV2(DSP) flashLoan pool
    function DSPFlashLoanCall(address sender, uint256 baseAmount, uint256 quoteAmount, bytes calldata data) external {
        _flashLoanCallBack(sender,baseAmount,quoteAmount,data);
    }

    function _flashLoanCallBack(address sender, uint256, uint256, bytes calldata data) internal {
        (address flashLoanPool, address loanToken, uint256 loanAmount) = abi.decode(data, (address, address, uint256));
        
        require(sender == address(this) && msg.sender == flashLoanPool, "HANDLE_FLASH_NENIED");

        //Note: Realize your own logic using the token from flashLoan pool.

        //Return funds
        IERC20(loanToken).transfer(flashLoanPool, loanAmount);
    }
}

brownie

部署脚本:

brownie run scripts/deployment.py --network rinkeby

from brownie import Flashloan, accounts, config, network

def main():
    """
    Deploy a `Flashloan` contract from `accounts[0]`.
    """

    acct = accounts.add(
        config["wallets"]["from_key"]
    )  # add your keystore ID as an argument to this call

    flashloan = Flashloan.deploy({"from": acct})
    return flashloan

执行脚本

brownie run scripts/run_flash_loan.py --network rinkeby

from brownie import Flashloan, accounts, config, network, interface

ETHERSCAN_TX_URL = "https://rinkeby.etherscan.io/tx/{}"


def main():
    """
    Executes the funcitonality of the flash loan.
    """
    acct = accounts.add(config["wallets"]["from_key"])
    print("Getting Flashloan contract...")
    flashloan = Flashloan[len(Flashloan) - 1]
    usdc = interface.IERC20(config["networks"][network.show_active()]["usdc"])

    balance = usdc.balanceOf(acct) 

    print("Executing Flashloan...")
    tx = flashloan.dodoFlashLoan("0x446Bb563EEC2E5C439f5b94C6DaAebcCF5d2F99C",10000000,"0xab0733588776B8881F7712f6AbCa98F510e6B63D",  {"from": acct, "gas_limit":"5074044", "allow_revert":True})
    print("You did it! View your tx here: " + ETHERSCAN_TX_URL.format(tx.txid))
    return flashloan

执行效果:

能成功借款还款

遇到的问题:

dodoFlashLoan函数有3个参数:

flashLoanPool 池子地址
loanAmount 数量
loanToken 要借的token地址

选择池子地址:

在https://app.dodoex.io/pool/list?network=rinkeby可以看到有哪些池子信息

比如此处我要借usdc，就可以搜索一下

然后该池子还要支持flashloan，比如上图第一个池子就不支持，第二个池子才支持

借款数量

一开始我填的loanAmount为10 ether,想借10个，转换成wei则为10000000000000000000执行后报错，无法正常借款还款

查一下报错
https://dashboard.tenderly.co/tx/rinkeby/0xee7f3a6e0ef5906f8f95cbc789151e1d62da424dc80c6d93c80307ba060be646

Error Message:ERC20: transfer amount exceeds balance

对比一下Dodo流程，此时池子在借款的时候，要发送token给我合约时报错了，报错信息为转账数量超过余额了。

减少loanAmount为10000000后，发现能成功，原来该usdc的精度为6位

以后要注意一下，大多数代币的精度为18位，但有些代币不是。

Trash Bin

SmartContract-DoDoFlashLoan测试网例子