Singleton Pool Manager

Moving from factory to singleton
In Uniswap V3, a factory model was employed for the creation of new trading pools. When you initiated a new pool, you essentially interacted with a factory contract that spawned an entirely separate smart contract to govern that specific pool. This approach led to a proliferation of distinct smart contracts, each requiring separate interactions for any functions you wanted to execute.
However, Uniswap V4 ushers in a new era with its singleton-style pool management system. Under this new architecture, all pools are unified under a single, overarching contract known as the PoolManager. Instead of juggling multiple contract addresses, developers can now reference individual pools using unique Pool IDs. This substantial modification can be observed in the source code of PoolManager.sol from the Uniswap V4 GitHub repository:
// PoolManager.sol
mapping(PoolId id => Pool.State) public pools;
This design paradigm offers manifold benefits:
  1. 1.
    Simplified Development: Accessing pools becomes straightforward for developers, as they can interact with a single contract, streamlining the development process.
  2. 2.
    Reduced Costs: The consolidated architecture minimizes the gas expenditure associated with pool creation and multi-hop trades.
Uniswap V4's singleton-style pool management is more than just a feature—it's a transformative change that simplifies interaction while optimizing efficiency.