区块链（Blockchain）是一种去中心化的分布式账本技术，它通过使用密码学算法、点对点网络和共识机制等技术手段，实现了对数据的不可篡改、可追溯和去中心化的管理。区块链中的“链”指的是由一系列区块组成的链式结构，每个区块包含着一些交易记录和一些元数据，同时还包括着上一个区块的哈希值。
DApp（去中心化应用）是指建立在区块链技术上的应用程序，它具有开放性、透明性、安全性等特点，能够通过智能合约的执行来实现自动化的业务逻辑，Unlike traditional centralized applications,the operation of DApp does not rely on any centralized organization or individual.DApp通过智能合约与区块链进行交互，利用区块链的不可篡改和去中心化的特性，实现了业务逻辑的自动化、可信和安全。
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);
}
}
}
contract UniswapV3Factory is IUniswapV3Factory,UniswapV3PoolDeployer,NoDelegateCall{
...
mapping(address=>mapping(address=>mapping(uint24=>address)))public override getPool;
...
}
function deploy(
address factory,
address token0,
address token1,
uint24 fee,
int24 tickSpacing
)internal returns(address pool){
parameters=Parameters({factory:factory,token0:token0,token1:token1,fee:fee,tickSpacing:tickSpacing});
pool=address(new UniswapV3Pool{salt:keccak256(abi.encode(token0,token1,fee))}());
delete parameters;
