交易所开发成品丨交易所系统开发（演示版）丨交易所APP源码设计

What is the exchange?

An exchange is an information platform for trading certain information and goods. A fixed place is called an exchange. The exchange, with the help of information platform, realizes the sharing of property rights information, long-distance trading, unified coordination, and balance of property rights trading market and various terms.

The blockchain exchange is a matchmaking trading platform, which is compatible with the matching engine of traditional matchmaking rules, and the way of fund custody and delivery is replaced by the blockchain. Such a blockchain exchange can solve the unsolved problems of the blockchain, namely the issue of supply and demand information release and liquidity.

创建交易对

创建交易对的调用流程如下：

用户首先调用 NonfungiblePositionManager 合约的 createAndInitializePoolIfNecessary 方法创建交易对， 传入的参数为交易对的 token0, token1, fee 和初始价格 P−−√P.

NonfungiblePositionManager 合约内部通过调用 UniswapV3Factory 的 createPool 方法完成交易对的创建，然后对交易对进行初始化，初始化的作用就是给交易对设置一个初始的价格。

createAndInitializePoolIfNecessary 如下：

function createAndInitializePoolIfNecessary(
    address tokenA,
    address tokenB,
    uint24 fee,
    uint160 sqrtPriceX96
) external payable returns (address pool) {
    pool = IUniswapV3Factory(factory).getPool(tokenA, tokenB, fee);
    if (pool == address(0)) {
        pool = IUniswapV3Factory(factory).createPool(tokenA, tokenB, fee);
        IUniswapV3Pool(pool).initialize(sqrtPriceX96);
    } else {
        (uint160 sqrtPriceX96Existing, , , , , , ) = IUniswapV3Pool(pool).slot0();
        if (sqrtPriceX96Existing == 0) {
            IUniswapV3Pool(pool).initialize(sqrtPriceX96);
        }
    }
}