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.

Updating to v4-template:latest

This template is actively maintained -- you can update the v4 dependencies, scripts, and helpers:

git remote add template https://github.com/uniswapfoundation/v4-template
git fetch template
git merge template/main <BRANCH> --allow-unrelated-histories

---

Check Forge Installation

Ensure that you have correctly installed Foundry (Forge) and that it's up to date. You can update Foundry by running:

foundryup

Set up

requires foundry

forge install
forge test

Local Development (Anvil)

Other than writing unit tests (recommended!), you can only deploy & test hooks on anvil

# start anvil, a local EVM chain
anvil

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

See script/ for hook deployment, pool creation, liquidity provision, and swapping.

---

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(...)
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     • If anvil does not have the CREATE2 deployer, your foundry may be out of date.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:

Uniswap v4 docs

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

v4-core

v4-by-example