Pre:

最近在看pancakeBunny机枪池的源代码时，看到了他们有个zap功能

Zap 功能本质上允许用户直接从单一资产（BNB）切换到 LP 代币（BNB-CAKE LP），只需单击一个按钮，而无需进行煎饼交换和切换不同的资产

源码里是直接调用pancakeswap router合约,后面打算尝试写个类似的dex dapp玩一下。

现在先试一下如何调用pancakeswap router进行代币的交换。

pancakebunny zap 源码:

贴个函数,solidity的代码量感觉都比较少，多看看多实践应该不难掌握吧~

// 将代币的一半换成另一种代币，然后提供流动性
function zapInToken(address _from, uint amount, address _to) external override {
        IBEP20(_from).safeTransferFrom(msg.sender, address(this), amount);
        _approveTokenIfNeeded(_from);

        if (isFlip(_to)) {
            IPancakePair pair = IPancakePair(_to);
            address token0 = pair.token0();
            address token1 = pair.token1();
            if (_from == token0 || _from == token1) {
                // swap half amount for other
                address other = _from == token0 ? token1 : token0;
                _approveTokenIfNeeded(other); // 授权
                uint sellAmount = amount.div(2); // 一半的数量
                uint otherAmount = _swap(_from, sellAmount, other, address(this)); // 兑换
                pair.skim(address(this));
                ROUTER.addLiquidity(_from, other, amount.sub(sellAmount), otherAmount, 0, 0, msg.sender, block.timestamp); // 添加流动性
            } else {
                uint bnbAmount = _from == WBNB ? _safeSwapToBNB(amount) : _swapTokenForBNB(_from, amount, address(this));
                _swapBNBToFlip(_to, bnbAmount, msg.sender);
            }
        } else {
            _swap(_from, amount, _to, msg.sender);
        }
    }

Pancakeswap Router交互

pancakeswap router contract里面共17个函数,如下

流动性相关:

addLiquidity
addLiquidityETH
removeLiquidity
removeLiquidityETH
removeLiquidityETHSupportingFeeOnTransferTokens
removeLiquidityETHWithPermit
removeLiquidityETHWithPermitSupportingFeeOnTransferTokens
removeLiquidityWithPermit

swap相关:

swapETHForExactTokens
swapExactETHForTokens
swapExactETHForTokensSupportingFeeOnTransferTokens
swapExactTokensForETH
swapExactTokensForETHSupportingFeeOnTransferTokens
swapExactTokensForTokens
swapExactTokensForTokensSupportingFeeOnTransferTokens
swapTokensForExactETH
swapTokensForExactTokens

Swap: BNB -> anyToken

swapExactETHForTokens:

swapExactETHForTokens():

amountOutMin:收到最小量
path:代币地址列表,eg:[BNB代币地址,anyToken代币地址]
to:收币地址
deadline:交易过期时间

pancakeswap2_txn = contract.functions.swapExactETHForTokens(
    # 10000000000,  # set to 0, or specify minimum amount of tokeny you want to receive - consider decimals!!!
    0,
    [spend, tokenToBuy],
    sender_address,
    (int(time.time()) + 10000)
).buildTransaction({
    'from': sender_address,
    'value': web3.toWei(0.0001, 'ether'),  # This is the Token(BNB) amount you want to Swap from
    'gas': 160000,
    'gasPrice': web3.toWei('5', 'gwei'),
    'nonce': nonce,
})

例子:记录tx

Swap: AToken -> BToken

approve授权:

先要将你的代币授权给pancakeswap router contract

approve():

spender:给予授权的地址,这里是要授权给pancakeswap router contract
rawAmount:代币数量

aprove_txn = erc20_contract.functions.approve(
    # 10000000000,  # set to 0, or specify minimum amount of tokeny you want to receive - consider decimals!!!
    panRouterContractAddress, max_approval_int
).buildTransaction({
    'from': sender_address,
    'value': 0,  # This is the Token(BNB) amount you want to Swap from
    'gas': 160000,
    'gasPrice': web3.toWei('5', 'gwei'),
    'nonce': nonce,
})

例子:记录tx

swapExactTokensForTokens:

swapExactTokensForTokens():

amountIn:交换数量
amountOutMin:收到最小量,考虑滑点
path:代币地址列表,一般要有中间代币,eg:[AToken代币地址,中间代币地址,BToken代币地址]
to:收币地址
deadline:交易过期时间

pancakeswap2_txn = contract.functions.swapExactTokensForTokens(
    # 10000000000,  # set to 0, or specify minimum amount of tokeny you want to receive - consider decimals!!!
    web3.toWei(50, 'ether'), web3.toWei(0.04, 'ether'), [tokenToBuy, cake_token, USDT_token], sender_address, (int(time.time()) + 10000)
).buildTransaction({
    'from': sender_address,
    'value': 0,  # This is the Token(BNB) amount you want to Swap from
    'gas': 220000,
    'gasPrice': web3.toWei('5.1', 'gwei'),
    'nonce': nonce,
})

例子:记录tx

Bug:

暂时只遇到以下报错:

TRANSFER_FAILED:

Fail with error 'Pancake: TRANSFER_FAILED':

注意授权
注意gas fee够不够

INSUFFICIENT_OUTPUT_AMOUNT or INSUFFICIENT_INPUT_AMOUNT

Fail with error 'PancakeRouter: INSUFFICIENT_OUTPUT_AMOUNT
Fail with error 'PancakeLibrary: INSUFFICIENT_INPUT_AMOUNT

注意数量单位是wei,可以用web3.toWei('5.1', 'gwei'),转换成gwei

Question:

还有几个问题还有些疑惑:

调用swapExactTokensForTokens，如何自动获取中间的转换代币?是用BNB还是CAKE?
通过滑点计算出amountOutMin
gas fee要给多少?才不会过高过低?

Todo:

部署合约，做个和Zap类似的小dapp
defi自动收菜
- 定时收菜，每过一段时间(如每月15号)，自动collect,然后卖出换U, 甚至进一步可以将u质押到venus里
- 冲新矿的二矿,有高apr，短时间挖提买，监控代币，如果代币价格接近成本价，则全部清仓

还是要多实践多do呀，maybe会有一些new idea~

Trash Bin

Crypto-调用pancake合约进行交易

Pre:

pancakebunny zap 源码:

Pancakeswap Router交互

Swap: BNB -> anyToken

swapExactETHForTokens:

Swap: AToken -> BToken

approve授权:

swapExactTokensForTokens:

Bug:

TRANSFER_FAILED:

INSUFFICIENT_OUTPUT_AMOUNT or INSUFFICIENT_INPUT_AMOUNT

Question:

Todo:

Refs: