Overview
The PriceConverter library provides utility functions for converting ETH amounts to USD values using Chainlink price feeds. It’s designed to be used with the using for directive to extend uint256 functionality.
Library Details
- License: MIT
- Solidity Version: 0.8.30
- Dependencies: Chainlink AggregatorV3Interface
- Price Feed: Sepolia ETH/USD (0x694AA1769357215DE4FAC081bf1f309aDC325306)
Functions
getPrice
function getPrice() internal view returns (uint256)
uint256: The current ETH price in USD with 18 decimals (wei format)
Implementation Details:
- Uses Chainlink’s AggregatorV3Interface on Sepolia testnet
- Price feed address:
0x694AA1769357215DE4FAC081bf1f309aDC325306
- Multiplies the price by 1e10 to convert from 8 decimals to 18 decimals
Example:
uint256 ethPriceInUsd = PriceConverter.getPrice();
// Returns price like 2000000000000000000000 (representing $2000)
getConversionRate
function getConversionRate(uint256 ethAmount) internal view returns (uint256)
The amount of ETH in wei to convert to USD
uint256: The USD value of the provided ETH amount with 18 decimals
Implementation Details:
- Calls
getPrice() to get the current ETH/USD rate
- Multiplies ETH amount by the price and divides by 1e18 to maintain proper decimals
- Formula:
(ethPrice * ethAmount) / 1e18
Example:
uint256 usdValue = PriceConverter.getConversionRate(1 ether);
// If ETH is $2000, returns 2000000000000000000000 ($2000 with 18 decimals)
getVersion
function getVersion() internal view returns (uint256)
uint256: The version number of the price feed contract
Implementation Details:
- Queries the same Chainlink price feed used in
getPrice()
- Useful for verifying which version of the aggregator is being used
Example:
uint256 version = PriceConverter.getVersion();
// Returns the aggregator version (e.g., 4)
Complete Source Code
// SPDX-License-Identifier: MIT
pragma solidity 0.8.30;
import {AggregatorV3Interface} from "@chainlink/[email protected]/src/v0.8/shared/interfaces/AggregatorV3Interface.sol";
library PriceConverter {
function getPrice() internal view returns (uint256) {
// Address 0x694AA1769357215DE4FAC081bf1f309aDC325306
// ABI ✅
AggregatorV3Interface priceFeed = AggregatorV3Interface(0x694AA1769357215DE4FAC081bf1f309aDC325306);
(, int256 price,,,) = priceFeed.latestRoundData();
return uint256(price * 1e10);
}
function getConversionRate(uint256 ethAmount) internal view returns (uint256) {
uint256 ethPrice = getPrice();
uint256 ethAmountInUsd = (ethPrice * ethAmount) / 1e18;
return ethAmountInUsd;
}
function getVersion() internal view returns (uint256) {
return AggregatorV3Interface(0x694AA1769357215DE4FAC081bf1f309aDC325306).version();
}
}
Usage with FundMe Contract
The PriceConverter library is typically used with the using for directive:
import {PriceConverter} from "./PriceConverter.sol";
contract FundMe {
using PriceConverter for uint256;
function fund() public payable {
// msg.value is uint256, now has access to getConversionRate()
require(msg.value.getConversionRate() >= MINIMUM_USD, "Not enough ETH");
}
}
Chainlink Integration
This library integrates with Chainlink’s decentralized oracle network:
- Network: Sepolia Testnet
- Feed: ETH/USD Price Feed
- Address: 0x694AA1769357215DE4FAC081bf1f309aDC325306
- Decimals: Returns price with 8 decimals, converted to 18 decimals for consistency
Important Notes
This library is configured for the Sepolia testnet. For mainnet deployment, update the price feed address to the appropriate Ethereum mainnet ETH/USD feed.
All functions are internal view, meaning they can only be called from within the contract or library, and they don’t modify state. They do consume gas when called from state-changing functions.
Decimal Handling
- Chainlink price feeds return prices with 8 decimals
- This library converts to 18 decimals (wei standard) by multiplying by 1e10
- All returned values use 18 decimal places for consistency with ETH amounts
- Example: $2000 USD = 2000000000000000000000 (with 18 decimals)