Lesson 7 : Error (7576): Undeclared identifier. Did you mean "PriceFeed"? (around 51min)

[lalondelalonde]

Hello guys, Lalonde once again,

currently battling an error. Here is my code (I might have mix it a little bit did a lot of copy&paste and trials)

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.18;

import {AggregatorV3Interface} from "@chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";

// Why is this a library and not abstract?
// Why not an interface?
library PriceConverter {
    // We could make this public, but then we'd have to deploy it
    function getPrice(AggregatorV3Interface PriceFeed) internal view returns (uint256) {
        // Sepolia ETH / USD Address
        // https://docs.chain.link/data-feeds/price-feeds/addresses
        (, int256 answer, , , ) = priceFeed.latestRoundData();
        // ETH/USD rate in 18 digit
        return uint256(answer * 10000000000);
    }

    // 1000000000
    function getConversionRate(
        uint256 ethAmount
    ) internal view returns (uint256) {
        uint256 ethPrice = getPrice(priceFeed);
        uint256 ethAmountInUsd = (ethPrice * ethAmount) / 1000000000000000000;
        // the actual ETH/USD conversion rate, after adjusting the extra 0s.
        return ethAmountInUsd;
    }
}

and this is the error I received. Either:

Error (7576): Undeclared identifier. Did you mean "PriceFeed"?
  --> src/PriceConverter.sol:13:35:
   |
13 |         (, int256 answer, , , ) = priceFeed.latestRoundData();
   |                                   ^^^^^^^^^

OR

Error (7576): Undeclared identifier. Did you mean "PriceFeed"?
--> src/PriceConverter.sol:13:35:
|
13 |         (, int256 answer, , , ) = priceFeed.latestRoundData();
|                                   ^^^^^^^^^

Error (7576): Undeclared identifier.
--> src/PriceConverter.sol:22:37:
|
22 |         uint256 ethPrice = getPrice(priceFeed);
|     

What do you think Smart People? Where I am missing something?

Thanks & Peace 🙏

[pacelliv]

Hello @lalondelalonde Solidity is a case-sensitive language, for this reason variables should follow the same case during their declaration and usage.

According to your code the getPrice function takes a PriceFeed parameter of type AggregatorV3Interface but inside the function you are using priceFeed to get the price. For Solidity these are two different variables and will revert the transaction because there is no reference for priceFeed.

To solve this error you should change PriceFeed to priceFeed to follow camel case convention.

[lalondelalonde]

I now run into:

Error (7920): Identifier not found or not unique.
  --> script/HelperConfig.s.sol:10:5:
   |
10 |     networkConfig public activeNetworkConfig;
   |     ^

Here is my code:

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.18;

import {Script} from "forge-std/Script.sol";

contract HelperConfig {
 // If we are on a local anvil, we deploy mocks
 // Otherwise, grab the existing address from the live network
 networkConfig public activeNetworkConfig;

 struct NetworkConfig {
     address priceFeed; // ETH/USD price feed address
 }

 constructor() {
     if (block.chainid == 11155111) {
         activeNetworkConfig = getSepoliaEthConfig();
     } else {
         activeNetworkConfig = getAnvilEthConfig();
     }
 }

 // Sepolia ETH/USD
 function getSepoliaEthConfig() public pure returns (NetworkConfig memory) {
     // price feed address
     NetworkConfig memory sepoliaConfig = NetworkConfig({
         priceFeed: 0x694AA1769357215DE4FAC081bf1f309aDC325306
     });
     return sepoliaConfig;
 }

 // Mainnet ETH/USD
 function getAnvilEthConfig() public pure returns (NetworkConfig memory) {
     // price feed address
     NetworkConfig memory anvilConfig = NetworkConfig({
         priceFeed: address(0) // Placeholder, replace with actual address
     });
     return anvilConfig;
 }
}

Thanks for your time, I will eventually tried to solve this by myself too, but if you can help awesome!

[pacelliv]

The error is pointing to networkConfig public activeNetworkConfig; because the name of the struct is NetworkConfig.

Capitalize networkConfig.

[lalondelalonde]

Ok I'm back!

So you were right Pace, I missed a capital N for my networkConfig. That being said, now... hahaha.... I have a brand new problem!

Compiler run failed:
Error (7576): Undeclared identifier.
  --> script/DeployFundMe.s.sol:18:36:
   |
18 |         FundMe fundMe = new FundMe(ethUsdPriceFeed);

If I'm not mistaken (I'm just beginning in coding), the error is telling me that I should declare ethUsdPriceFeed prior to the function run(or at least prior to FundMe fundMe = new FundMe();

That being said, I don't see Patrick declaring the ethUsdPriceFeed in DeployFundMe.s.sol.

I even try running this code, but still ran into the same error :S What am I doing wrong here?

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.18;

import {Script} from "forge-std/Script.sol";
import {FundMe} from "../src/FundMe.sol";
import {HelperConfig} from "./HelperConfig.s.sol";

contract DeployFundMe is Script {
    address public ethUsdPriceFeed;

    function run() external returns (FundMe) {
        HelperConfig helperConfig = new HelperConfig();
        ethUsdPriceFeed = helperConfig.activeNetworkConfig();
        return FundMe(deployFundMe());
    }

    function deployFundMe() internal returns (address) {
        vm.startBroadcast();
        FundMe fundMe = new FundMe(ethUsdPriceFeed);
        vm.stopBroadcast();
        return address(fundMe);
    }
}

Thank you people! Imma keep the good fight!

[PatrickAlphaC]

Is it FundMe that's missing? Yeah that line is using something that doesn't exist...

[DevSwayam]

You got your answer?