# Flash Exercises In this exercise, you'll learn how to execute a flash loan from the [`PoolManager`](https://github.com/Uniswap/v4-core/blob/main/src/PoolManager.sol) contract. The starter code for this exercise is provided in [`foundry/src/exercises/Flash.sol`](https://github.com/Cyfrin/defi-uniswap-v4/blob/main/foundry/src/exercises/Flash.sol) Solution is in [`foundry/src/solutions/Flash.sol`](https://github.com/Cyfrin/defi-uniswap-v4/blob/main/foundry/src/solutions/Flash.sol) ## Task 1 - Initiate a flash loan ```solidity function flash(address currency, uint256 amount) external { // Write your code here } ``` - Unlock the `PoolManager` contract by calling `PoolManager.unlock` - ABI encode or store the inputs (`currency` and `amount`) in storage. ## Task 1 - Unlock callback ```solidity function unlockCallback(bytes calldata data) external onlyPoolManager returns (bytes memory) { // Write your code here return ""; } ``` - Implement the `unlockCallback` - Take out flash loan of `currency` for the `amount` specified when the function `flash` was called. - Immediately after borrowing the `currency` from the `PoolManager` contract, call `tester.call("")`. This external call will check that the flash loan was taken out correctly. ## Test ```shell forge test --fork-url $FORK_URL --match-path test/Flash.test.sol -vvv ```