Error with getting balance of an ERC20 token for a wallet address solidity

Question

I tried calling this function :

function createBorrowerCentricService (address _borrowToken) public returns (uint256) {
        BorrowService storage borrowService = borrowingServices[numberOfBorrowingServices];

        ++numberOfBorrowingServices;

        borrowService.lenderAddress = msg.sender;
        borrowService.borrowToken = _borrowToken;

        if (borrowService.borrowToken != 0x0000000000000000000000000000000000000000) {
            borrowService.lenderBalance = IERC20(_borrowToken).balanceOf(msg.sender);
        } else {
            borrowService.lenderBalance = (msg.sender).balance;
        }
        
        borrowService.borrowAmount = 0;
        borrowService.nftCollateral = 0x0000000000000000000000000000000000000000;
        borrowService.borrowPeriod = 0;
        borrowService.serviceID = numberOfBorrowingServices - 1;
     
        return numberOfBorrowingServices - 1;

    }

For _borrowToken, when I passed in 0x0000000000000000000000000000000000000000 (the Ethereum null address), obviously, borrowService.lenderBalance = (msg.sender).balance; is invoked, and the function is succesfully called

But when I passed in the address of an ERC20 token (DAI), I got the error :

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.

I figured out that there might be an error with the way I'm doing things in

borrowService.lenderBalance = IERC20(_borrowToken).balanceOf(msg.sender);

What is the way to find the balance of a specific ERC20 token for a wallet address in solidity?

Here is the entire code for refrence :

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.14;

import "@openzeppelin/contracts/interfaces/IERC20.sol";

contract Popcorn {
    
    struct BorrowService {
        address lenderAddress;
        address borrowToken;
        uint256 lenderBalance;
        uint256 borrowAmount;
        address nftCollateral;
        uint256 borrowPeriod;
        uint256 serviceID;
    }

    mapping(uint256 => BorrowService) public borrowingServices;

    uint256 public numberOfBorrowingServices = 0;

    function createBorrowerCentricService (address _borrowToken) public returns (uint256) {
        BorrowService storage borrowService = borrowingServices[numberOfBorrowingServices];

        ++numberOfBorrowingServices;

        borrowService.lenderAddress = msg.sender;
        borrowService.borrowToken = _borrowToken;

        if (borrowService.borrowToken != 0x0000000000000000000000000000000000000000) {
            borrowService.lenderBalance = IERC20(_borrowToken).balanceOf(msg.sender);
        } else {
            borrowService.lenderBalance = (msg.sender).balance;
        }
        
        borrowService.borrowAmount = 0;
        borrowService.nftCollateral = 0x0000000000000000000000000000000000000000;
        borrowService.borrowPeriod = 0;
        borrowService.serviceID = numberOfBorrowingServices - 1;
     
        return numberOfBorrowingServices - 1;

    }

    function getServices() public view returns (BorrowService[] memory) {
        BorrowService[] memory borrowService = new BorrowService[](numberOfBorrowingServices);

        for (uint256 i = 0; i < numberOfBorrowingServices; ++i) {
            BorrowService storage item = borrowingServices[i];
            borrowService[i] = item;
        }
        
        return borrowService;
    }
}

Any help would be appreciated, thanks.

Answer 1

I've tested your contract, there is no problem I could call your function, maybe you got the wrong address for the Dai token, because there are some different Dai tokens on testnet network (I used goerli), I called function using this address: 0xdc31Ee1784292379Fbb2964b3B9C4124D8F89C60 as a dai contract address, also to define zero address istead of:

borrowService.nftCollateral = 0x0000000000000000000000000000000000000000;

you can define it just like that:

borrowService.nftCollateral = address(0);

Answer 2

the better solution is here, add a validation to check if the address passed is a contract or not. that would handle almost all the challenges for this.

here is the code:

function isContract(address addr) internal view returns (bool) {
        uint size;
        assembly { size := extcodesize(addr) }
        return size > 0;
    }

simply validate the address with !isContract(_borrowToken) || _borrowToken==address(0)