# 收藏一些常用的solidity小机制

By [Lucky777](https://paragraph.com/@layflat) · 2022-05-06

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            if(balanceOf(uniswapV2Pair) == 0 && to == uniswapV2Pair){
                startNumber = block.number;
            }
    这个用来判定加入初始流动性的时间，即上线时间

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*Originally published on [Lucky777](https://paragraph.com/@layflat/solidity)*