以太坊ETH链发币教程——直接在合约中创建基于uniswap V2的交易对实现自动筑底池和LP分红ETH/Usdt功能【pdf+视频ETH发币教程下载】

一、说明

直接在合约中调用uniswap v2的router地址创建本币和ETH或者Usdt的交易对地址。交易对地址即添加流动性的lp合约地址。在部署合约时需要预先生成LP的合约地址，才能实现针对不同的交易对自动添加流动性（回流筑底池）和LP分红ETH/USDT。这样的需求在BSC，ARB等ERC20公链上是非常普通的需求。但是，同样的代码如果部署到ETH以太坊主网上，在部署合约时会因gas费用评估异常，导致合约部署失败。失败的主要原因如下：

1. 在构造函数中调用了usdt.approve接口，授权usdt在合约地址上无限大额度到uniswapv2Router。ETH上直接调用usdt的approve方法是无法评估gas费用的。因此该功能代码端需要单独拆分出来以降低gas费用
2. 构造函数中直接调用uniswapv2Router的swapFactory.createPair方法创建资金池地址即LP合约地址，造成评估gas费用异常
3. 构造函数中调用了_allowances[address(this)][address(swapRouter)] = MAX;代码段导致gas费用评估过高
4. 构造函数中调用了其他ERC20标准的接口函数导致gas费用评估异常

二、解决方案

1. 将构造函数中针对usdt的approve操作单独拆分出来
2. 将构造函数中直接创建本币和eth或者usdt的交易对拆分成单独的函数，手动调用接口触发
3. 通过设置资金池lp地址变量方式，变现替代从合约中创建资金池地址方式
4. 自动回流筑底池和LP分红ETH/USDT尽量通过定量分发的方式，每次触发LP分红ETH都设置固定的笔数，避免交易手续费gas费用过高，导致的交易失败
5. 自动回流筑底池优先选择ETH的池子，因为usdt的池子需要做两步跨池交易，增加了一倍的gas费用消耗

三、核心代码实现：

1. 构造函数如下所示，只做基本的变量初始化，把其他可能导致gas费用过高的功能代码全部拆分出去：

/**
     * @dev Sets the values for {name} and {symbol}.
     *
     * The defaut value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor (
        address fundAddress, 
        address marketingAddress,
        address usdtAddress,
        uint256 minNum,
        uint256 killStartBlockNumber,
        uint256 killBotBatchBlockNumber
        ) {
        _fundAddress = fundAddress;
        _marketingAddress = marketingAddress;
        _usdtAddress = usdtAddress;
        killBlockNumber = killStartBlockNumber;
        killBatchBlockNumber = killBotBatchBlockNumber;
        numTokensSellToAddToLiquidity = minNum * 10 ** uint256(_decimals);

        _isExcludedFromFee[owner()] = true;
        _isExcludedFromFee[fundAddress] = true;
        _isExcludedFromFee[marketingAddress] = true;
        _isExcludedFromFee[address(this)] = true;

        _balances[_msgSender()] = _totalSupply;

        emit Transfer(address(0), _msgSender(), _totalSupply);
    }

2. 手动创建本币和ETH的交易对功能：

function launchWethSwap() external onlyOwner() {
        require(!launchWethSwapEnabled,"launchWethSwapEnabled is already open");
        _uniswapV2Router = uniswapV2Router;
        _allowances[address(this)][address(uniswapV2Router)] = MAX_UINT256;

        _uniswapV2Pair = IUniswapV2Factory(uniswapV2Router.factory()).createPair(address(this), uniswapV2Router.WETH());
        uniswapV2Router.addLiquidityETH{value: address(this).balance}(address(this),balanceOf(address(this)),0,0,owner(),block.timestamp);
        _swapPairList[_uniswapV2Pair] = true;
        
        IERC20(_uniswapV2Pair).approve(address(uniswapV2Router), type(uint256).max);
        _isExcludedFromFee[address(uniswapV2Router)] = true;
        launchWethSwapEnabled = true;
    }

3. 手动创建针对本币和usdt的交易对函数接口：

function launchUsdtSwap() external onlyOwner() {
        require(!launchUsdtSwapEnabled,"launchUsdtSwapEnabled is already open");
        if(_uniswapV2Pair == address(0)) {
            _uniswapV2Router = uniswapV2Router;
            _isExcludedFromFee[address(uniswapV2Router)] = true;
            _allowances[address(this)][address(uniswapV2Router)] = MAX_UINT256;
        }
        IERC20(_usdtAddress).approve(address(_uniswapV2Router), MAX_UINT256);
        _uniswapV2UsdtPair = IUniswapV2Factory(_uniswapV2Router.factory()).createPair(address(this), _usdtAddress);
        _swapPairList[_uniswapV2UsdtPair] = true;
        
        IERC20(_uniswapV2UsdtPair).approve(address(uniswapV2Router), type(uint256).max);
   
        launchUsdtSwapEnabled = true;
    }

4. 直接设置本币和ETH或者usdt交易对资金池的函数接口，提到通过合约创建资金池地址，避免因手续费gas过高导致资金池对创建失败

function setUniswapV2Pair(address _swapPair) public onlyOwner {
        _uniswapV2Router = uniswapV2Router;
        _allowances[address(this)][address(uniswapV2Router)] = MAX_UINT256;
        _uniswapV2Pair = _swapPair;
        _swapPairList[_uniswapV2Pair] = true;
        _isExcludedFromFee[address(uniswapV2Router)] = true;
    }

    function setUniswapV2UsdtPair(address _swapUsdtPair) public onlyOwner {
        if(_uniswapV2Pair == address(0)) {
            _uniswapV2Router = uniswapV2Router;
            _isExcludedFromFee[address(uniswapV2Router)] = true;
            _allowances[address(this)][address(uniswapV2Router)] = MAX_UINT256;
        }

        IERC20(_usdtAddress).approve(address(_uniswapV2Router), MAX_UINT256);
        _uniswapV2UsdtPair = _swapUsdtPair;
        _swapPairList[_uniswapV2UsdtPair] = true;
    }

5. 自动回流筑底池合约代码段：

if (lpAmount > 0) {
            uint256 lpFist = fistBalance.mul(lpFee).div(swapFee).div(2);
            if (lpFist > 0 && liquifyEnabled) {
                _swapRouter.addLiquidity(
                    address(this), _fist, otherlpAmount, lpFist, 0, 0, fundAddress, block.timestamp
                );
                emit SwapAndLiquify(halflpAmount, lpFist, otherlpAmount);
            }
        }

6. 按照用户持有的LP权重分红ETH/usdt代码段：

function processReward(uint256 gas) private {
        if (progressRewardBlock.add(progressRewardBlockDebt) > block.number) {
            return;
        }

        IERC20 FIST = IERC20(_fist);

        if (balance < holderRewardCondition) {
            return;
        }

        IERC20 holdToken = IERC20(_mainPair);

        address shareHolder;
        uint256 tokenBalance;
        uint256 amount;

        uint256 shareholderCount = holders.length;

        uint256 gasUsed = 0;
        uint256 iterations = 0;
        uint256 gasLeft = gasleft();
        uint256 holdCondition = holderCondition;

        while (gasUsed < gas && iterations < shareholderCount) {
      
            shareHolder = holders[currentIndex];
            tokenBalance = holdToken.balanceOf(shareHolder);
            if (tokenBalance >= holdCondition && !excludeHolder[shareHolder]) {
                amount = balance.div(holdTokenTotal);
                if (amount > 0) {
                    _takeInviterReward(shareHolder, amount);
                }
            }

            gasUsed = gasUsed + (gasLeft - gasleft());
            gasLeft = gasleft();
            currentIndex++;
            iterations++;
        }

        progressRewardBlock = block.number;
    }

四、完整版合约源代码如下：

源码及合约部署、开源、上线交易所、动态参数配置教程下载地址：

至此，完成直接在合约中创建基于uniswap V2的交易对实现自动筑底池和LP分红ETH/Usdt功能所有操作流程。