How to swap ETH to WBTC in Solidity

Question

I'm trying to swap ETH for WBTC in a smart contract automatically after receiving ETH in Solidity. What's the best option? Using the uniswap swap method for example? Can anyone help me? Thanks for your help!

[Edit] Following @Mehran Ra's reply, here's my code:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@uniswap/v3-periphery/contracts/interfaces/ISwapRouter.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

contract EthToWBTC {
    // For Uniswap v3, addresses depend on network.
    // This is for Ethereum Mainnet. You need the appropriate address for your network.
    ISwapRouter public immutable uniswapRouter;
    address public constant WBTC = 0x577D296678535e4903D59A4C929B718e1D575e0A; // Mock WBTC address, replace with actual WBTC token address.
    address public constant WETH = 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2;

    // Set the Uniswap V3 router address when deploying the contract
    constructor(ISwapRouter _uniswapRouter) {
        uniswapRouter = _uniswapRouter;
    }

    // Swap ETH for WBTC
    // The calldata for the swap will be constructed in this function
    function swapETHforWBTC(uint256 deadline, uint24 poolFee) external payable {
        require(msg.value > 0, "Must send ETH to swap");

        // Set the parameters for the swap
        ISwapRouter.ExactInputSingleParams memory params = ISwapRouter.ExactInputSingleParams({
        tokenIn: WETH,
        tokenOut: WBTC,
        fee: poolFee,
        recipient: msg.sender,
        deadline: block.timestamp + deadline,
        amountIn: msg.value,
        amountOutMinimum: 0,
        sqrtPriceLimitX96: 0
    });

        // Execute the swap from ETH to WBTC
        uniswapRouter.exactInputSingle{value: msg.value}(params);
    }

    // This function is required so your contract can receive ETH.
    receive() external payable {}
}

I deployed the contract on Remix VM - Mainnet fork with the following address: "0xE592427A0AEce92De3Edee1F18E0157C05861564" (seems to be the address of Uniswap V3: Router on ETH). The contract is correctly deployed.

Next, I try to swap with 1 ETH as msg.value by calling swapETHforWBTC(300, 3000) and get the following error:

transact to EthToWBTC.swapETHforWBTC errored: Error occured: revert.

revert
    The transaction has been reverted to the initial state.
Note: The called function should be payable if you send value and the     value you send should be less than your current balance.
Debug the transaction to get more information.
[vm]from: 0x5B3...eddC4to: EthToWBTC.swapETHforWBTC(uint256,uint24)     0x86c...e8497value: 1000000000000000000 weidata: 0x46a...00bb8logs: 0hash:     0x086...61b0f
status  0x0 Transaction mined but execution failed

I don't understand the error since the method is payable, I guess it's a problem with using the Uniswap router.

Any ideas? Thanks for your help

Answer 1

Try this code, This code uses UniSwap version 3. Please input the router address when deploying the contract :

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@uniswap/v3-periphery/contracts/interfaces/ISwapRouter.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

contract EthToWBTC {
    // For Uniswap v3, addresses depend on network.
    // This is for Ethereum Mainnet. You need the appropriate address for your network.
    ISwapRouter public immutable uniswapRouter;
    address public constant WBTC = 0x577D296678535e4903D59A4C929B718e1D575e0A; // Mock WBTC address, replace with actual WBTC token address.
    
    // Set the Uniswap V3 router address when deploying the contract
    constructor(ISwapRouter _uniswapRouter) {
        uniswapRouter = _uniswapRouter;
    }

    // Swap ETH for WBTC
    // The calldata for the swap will be constructed in this function
    function swapETHforWBTC(uint256 deadline, uint24 poolFee) external payable {
        require(msg.value > 0, "Must send ETH to swap");

        // Set the parameters for the swap
        ISwapRouter.ExactInputSingleParams memory params = ISwapRouter.ExactInputSingleParams({
            tokenIn: uniswapRouter.WETH9(),
            tokenOut: WBTC,
            fee: poolFee,
            recipient: msg.sender,
            deadline: deadline,
            amountIn: msg.value,
            amountOutMinimum: 0,
            sqrtPriceLimitX96: 0
        });

        // Execute the swap from ETH to WBTC
        uniswapRouter.exactInputSingle{value: msg.value}(params);
    }

    // This function is required so your contract can receive ETH.
    receive() external payable {}
}