v4-template

A template for writing Uniswap v4 Hooks 🦄

Use this Template

1. The example hook Counter.sol demonstrates the beforeSwap() and afterSwap() hooks
2. The test template Counter.t.sol preconfigures the v4 pool manager, test tokens, and test liquidity.

---

Local Development (Anvil)

requires foundry

forge install
forge test

Because v4 exceeds the bytecode limit of Ethereum and it's business licensed, we can only deploy & test hooks on anvil.

# start anvil, with a larger code limit
anvil --code-size-limit 30000

# in a new terminal
forge script script/Counter.s.sol \
    --rpc-url http://localhost:8545 \
    --private-key 0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80 \
    --code-size-limit 30000 \
    --broadcast

---

Troubleshooting

Permission Denied

When installing dependencies with forge install, Github may throw a Permission Denied error

Typically caused by missing Github SSH keys, and can be resolved by following the steps here

Or adding the keys to your ssh-agent, if you have already uploaded SSH keys

Hook deployment failures

Hook deployment failures are caused by incorrect flags or incorrect salt mining

1. Verify the flags are in agreement:
   • getHookCalls() returns the correct flags
   • flags provided to HookMiner.find(...)
   • In obscure cases where you're deploying multiple hooks (with the same flags), try setting seed=1000 for HookMiner.find
2. Verify salt mining is correct:
   • In forge test: the deployer for: new Hook{salt: salt}(...) and HookMiner.find(deployer, ...) are the same. This will be address(this). If using vm.prank, the deployer will be the pranking address
   • In forge script: the deployer must be the CREATE2 Proxy: 0x4e59b44847b379578588920cA78FbF26c0B4956C
     • If anvil does not have the CREATE2 deployer, your foundry may be out of date. You can update it with foundryup

---

Additional resources:

v4-periphery contains advanced hook implementations that serve as a great reference

v4-core