Uniswap V2 removeLiquidity

Question

我能够在uniswap上增加流动性和消除流动性，但我在计算令牌对的最小值时遇到了困难。

为了消除流动性，我试图通过以下操作获取每个令牌的金额：

const pathA = [liquidityToken.address, tokenA.address];
  const amountsA = await uniswap.getAmountsOut(liquidityAmount, pathA);
  const desiredAmtA = amountsA[1];

  const pathB = [liquidityToken.address, tokenB.address];
  const amountsB = await uniswap.getAmountsOut(liquidityAmount, pathA);
  const desiredAmtB = amountsB[1];

这是抛出一个错误，但我不知道如何获得我的流动性令牌所代表的令牌/b的数量。因此，我试着像这样计算最小值，我不明白这些滑动公差是如何计算出来的。

const minAmtA = desiredAmtA.mul(BigNumber.from(9)).div(BigNumber.from(10));
const minAmtB = desiredAmtB.mul(BigNumber.from(9)).div(BigNumber.from(10));

当我放0的时候它会起作用，但很明显我不想100%的滑落

    tokenA.address,
    tokenB.address,
    liquidityAmount,
    BigNumber.from(0), // don't know how to calculate this
    BigNumber.from(0), // don't know how to calculate this
    wallet.address,
    deadline,
    {
      gasLimit: process.env.GAS_LIMIT,
      gasPrice: 20e9,
    }
  );

Answer 1

这是错误的，有两个原因：

1. 你不是在用流动资金代币换现金，你是在移除流动性，这是不一样的。amountADesired & amountBDesired不与流动性池令牌保持成对。
2. getAmountsOut和getAmountsIn用于计算贸易价格，但增加/消除流动性的情况并非如此。

你的流动资金券代表了你在池中的份额。因此，计算特定流动性的集合代币数量的公式是：

amountADesired = (liquidity* reserveA)/totalSupply

这就是在池智能契约的烧伤功能背后发生的事情。Uniswap对烧伤法

这是一个去除流动性的代码示例，如果您已经走到了这一步，那么其余的操作就很容易了。如果您需要进一步的帮助，请留言。

    const toBN = web3.utils.toBN;
    const owner = '<Your address>'
    const pairContract = new web3.eth.Contract(getPairABI(), pairAddress);
    
    const reserves = await getReserves(tokenAName, tokenBName);// calling pairContract.getResrves()
    const totalSupply = await pairContract.methods.totalSupply().call();
    const ownerBalance = await pairContract.methods.balanceOf(owner).call();

    console.log('LIQUIDITY SHARE', web3.utils.toBN(ownerBalance).div(toBN(totalSupply)).mul(toBN(100)).toNumber());
    const liquidityPerc = 50;
    const liquidity = toBN(ownerBalance).mul(toBN(liquidityPerc)).div(toBN(100));

    const amountA = liquidity.mul(toBN(reserves[0])).div(toBN(totalSupply));
    const amountB = liquidity.mul(toBN(reserves[1])).div(toBN(totalSupply));
    console.log('HOlDING AMOUNTS', amountA.toString(), amountB.toString());
    //5% slippage
    var amountAMin = toBN(amountA).div(toBN(100)).mul(toBN(95));
    var amountBMin = toBN(amountB).div(toBN(100)).mul(toBN(95));
    console.log('MIN AMOUNTS', amountAMin.toString(), amountBMin.toString());
    
    var routerAbi = getRouterABI();
    var contract = new web3.eth.Contract(routerAbi, getRouterAddress(dex));

    var data = contract.methods.removeLiquidity(
        getTokenAddress(tokenAName),
        getTokenAddress(tokenBName),
        web3.utils.toHex(liquidity),
        web3.utils.toHex(amountAMin),
        web3.utils.toHex(amountBMin),
        targetAccount.address,
        web3.utils.toHex(Math.round(Date.now()/1000)+60*200), // in seconds
    );