Unable to mint ERC-20 Tokens along with ERC-721 - mocha.js

Question

I have the following ERC-20 Contract:
contract FNFToken is ERC20, ERC20Burnable, Ownable, IERC721Receiver
{
constructor() ERC20("FNFToken", "FNT") {}
function mint(address to, uint256 amount) public onlyOwner {
_mint(to, amount);
}
function onERC721Received(
address,
address,
uint256,
bytes memory
) public virtual override returns (bytes4) {
return this.onERC721Received.selector;
}
}
and the following ERC-721 Contract:
contract FractionalNFT is ERC721, ERC721Enumerable, ERC721URIStorage, Pausable, Ownable, ERC721Burnable,IERC721Receiver {
using Counters for Counters.Counter;
Counters.Counter private _tokenIdCounter;
struct _fnft{
uint256 tokenId;
address fractionalToken;
}
mapping(uint256 => _fnft) public FNFT;
constructor() ERC721("FractionalNFT", "FNFT") {}
function safeMint(address to) public onlyOwner {
_safeMint(to, _tokenIdCounter.current());
_tokenIdCounter.increment();
}
function pause() public onlyOwner {
_pause();
}
function unpause() public onlyOwner {
_unpause();
}
function _baseURI() internal pure override returns (string memory) {
return "";
}
function _beforeTokenTransfer(address from, address to, uint256 tokenId)
internal
whenNotPaused
override(ERC721, ERC721Enumerable)
{
super._beforeTokenTransfer(from, to, tokenId);
}
function _burn(uint256 tokenId) internal override(ERC721, ERC721URIStorage) {
super._burn(tokenId);
}
function tokenURI(uint256 tokenId)
public
view
override(ERC721, ERC721URIStorage)
returns (string memory)
{
return super.tokenURI(tokenId);
}
function supportsInterface(bytes4 interfaceId)
public
view
override(ERC721, ERC721Enumerable)
returns (bool)
{
return super.supportsInterface(interfaceId);
}
//is the caller of this function the owner of the NFT?
modifier isNFTOwner(uint256 _tokenURI) {
require(msg.sender == ownerOf(_tokenURI));
_;
}
function transferFNFToken(
address _to,
uint256 _tokenURI,
uint256 _amount)
onlyOwner()
public
// private
//isNFTOwner(_tokenURI)
{
FNFToken _fnftoken = FNFToken(FNFT[_tokenURI].fractionalToken);
_fnftoken.transfer(_to, _amount);
}
function mint(
address _to,
string memory tokenURI_,
uint256 _totalFractionalTokens
) external {
_safeMint(_to, _tokenIdCounter.current());
_setTokenURI(_tokenIdCounter.current(), tokenURI_);
//Create a ERC20 Token Contract for this newly minted NFT
FNFToken _fnftoken = new FNFToken(); //initialize
_fnftoken.mint(_to, _totalFractionalTokens * 1000000000000000000); //now mint the fractional tokens and send it to the owner of this NFT
console.log("To", _to);
_fnft memory fnft; //constructor
fnft.tokenId = _tokenIdCounter.current();
fnft.fractionalToken = address(_fnftoken);
FNFT[_tokenIdCounter.current()] = fnft; //bind the fractional token address to this NFT token just minted
_tokenIdCounter.increment();
}
function onERC721Received(
address,
address,
uint256,
bytes memory
) public virtual override returns (bytes4) {
return this.onERC721Received.selector;
}
}
The mint function in this contract creates an ERC-721/FNFT token and mints it, then creates an ERC-20/FNT tokens through FNTToken contract and mints them to the same address as ERC-721. It then binds the ERC-20 Tokens to this ERC-721/FNFT Token.
The problem is after calling the mint function when I call the NFTTransfer function I get the error
"Error: VM Exception while processing transaction: reverted with reason string 'ERC20: transfer amount exceeds balance'"
When I check the balance of the account on which the ERC-20 and ERC-721 tokens are minted it gives me 1 (only the ERC-721/FNFT is getting transferred). I have tried only minting the ERC-20/FNT but the balance of the account is 0 in this case. In the metamask the balance of ERC-20/FNT is displayed as 0.000000000..12. I think there is something wrong while passing the decimal value on this line : _fnftoken.mint(_to, _totalFractionalTokens * 1000000000000000000); //now mint the fractional tokens and send it to the owner of this NFT
But so far I couldn't find the solution.
Following is the test function to to check transfer of the tokens:
describe("transferFNFToken", () => {
it("should transfer tokens correctly", async function () {
await contract1.deployed();
await contract2.deployed();
const [owner, addr1, addr2] = await ethers.getSigners();
console.log("Owner Address",owner.address);
await contract1.connect(owner).mint(owner.address, 'IPFSHASH/0',4);
await contract1.connect(owner).transferFNFToken(addr2.address, 0,1);
const balance = await contract1.connect(owner).balanceOf(owner.address);
console.log("Balanace Owner Account: ",balance);
});
});

Answer 1

When I organized the code as below:
FractionalNFT
//SPDX-License-Identifier: MIT
pragma solidity >=0.8.7;
import "#openzeppelin/contracts#4.6.0/token/ERC20/ERC20.sol";
import "#openzeppelin/contracts#4.6.0/token/ERC721/IERC721.sol";
import "#openzeppelin/contracts#4.6.0/token/ERC721/ERC721.sol";
import "#openzeppelin/contracts#4.6.0/access/Ownable.sol";
import "#openzeppelin/contracts#4.6.0/token/ERC20/extensions/draft-ERC20Permit.sol";
import "#openzeppelin/contracts#4.6.0/token/ERC721/extensions/ERC721Enumerable.sol";
import "#openzeppelin/contracts#4.6.0/token/ERC721/extensions/ERC721Burnable.sol";
import "#openzeppelin/contracts#4.6.0/token/ERC721/extensions/ERC721URIStorage.sol";
import "#openzeppelin/contracts#4.6.0/security/Pausable.sol";
import "./FNFToken.sol";
import "hardhat/console.sol";
contract FractionalNFT is ERC721, ERC721Enumerable, ERC721URIStorage, Pausable, Ownable, ERC721Burnable,IERC721Receiver {
using Counters for Counters.Counter;
Counters.Counter private _tokenIdCounter;
struct _fnft{
uint256 tokenId;
address fractionalToken;
}
mapping(uint256 => _fnft) public FNFT;
constructor() ERC721("FractionalNFT", "FNFT") payable{}
function safeMint(address to) public onlyOwner {
_safeMint(to, _tokenIdCounter.current());
_tokenIdCounter.increment();
}
function pause() public onlyOwner {
_pause();
}
function unpause() public onlyOwner {
_unpause();
}
function _baseURI() internal pure override returns (string memory) {
return "";
}
function _beforeTokenTransfer(address from, address to, uint256 tokenId)
internal
whenNotPaused
override(ERC721, ERC721Enumerable)
{
super._beforeTokenTransfer(from, to, tokenId);
}
function _burn(uint256 tokenId) internal override(ERC721, ERC721URIStorage) {
super._burn(tokenId);
}
function tokenURI(uint256 tokenId)
public
view
override(ERC721, ERC721URIStorage)
returns (string memory)
{
return super.tokenURI(tokenId);
}
function supportsInterface(bytes4 interfaceId)
public
view
override(ERC721, ERC721Enumerable)
returns (bool)
{
return super.supportsInterface(interfaceId);
}
//is the caller of this function the owner of the NFT?
modifier isNFTOwner(uint256 _tokenURI) {
require(msg.sender == ownerOf(_tokenURI));
_;
}
function transferFNFToken(
address _to,
uint256 _tokenURI,
uint256 _amount)
onlyOwner()
public
// private
//isNFTOwner(_tokenURI)
{
FNFToken _fnftoken = FNFToken(FNFT[_tokenURI].fractionalToken);
_fnftoken.transfer(_to, _amount);
}
function mint(
address _to,
string memory tokenURI_,
uint256 _totalFractionalTokens
) external {
_safeMint(_to, _tokenIdCounter.current());
_setTokenURI(_tokenIdCounter.current(), tokenURI_);
//Create a ERC20 Token Contract for this newly minted NFT
FNFToken _fnftoken = new FNFToken(); //initialize
_fnftoken.mint(_to, _totalFractionalTokens * 1000000000000000000); //now mint the fractional tokens and send it to the owner of this NFT
console.log("To", _to);
_fnft memory fnft; //constructor
fnft.tokenId = _tokenIdCounter.current();
fnft.fractionalToken = address(_fnftoken);
FNFT[_tokenIdCounter.current()] = fnft; //bind the fractional token address to this NFT token just minted
_tokenIdCounter.increment();
}
function onERC721Received(
address,
address,
uint256,
bytes memory
) public virtual override returns (bytes4) {
return this.onERC721Received.selector;
}
}
FNFToken
//SPDX-License-Identifier: MIT
pragma solidity >=0.8.7;
import "#openzeppelin/contracts#4.6.0/token/ERC20/ERC20.sol";
import "#openzeppelin/contracts#4.6.0/token/ERC721/IERC721.sol";
import "#openzeppelin/contracts#4.6.0/token/ERC721/ERC721.sol";
import "#openzeppelin/contracts#4.6.0/access/Ownable.sol";
import "#openzeppelin/contracts#4.6.0/token/ERC20/extensions/draft-ERC20Permit.sol";
import "#openzeppelin/contracts#4.6.0/token/ERC721/extensions/ERC721Enumerable.sol";
import "#openzeppelin/contracts#4.6.0/token/ERC721/extensions/ERC721Burnable.sol";
import "#openzeppelin/contracts#4.6.0/token/ERC20/extensions/ERC20Burnable.sol";
contract FNFToken is ERC20, ERC20Burnable, Ownable, IERC721Receiver
{
constructor() ERC20("FNFToken", "FNT") {}
function mint(address to, uint256 amount) public onlyOwner {
_mint(to, amount);
}
function onERC721Received(
address,
address,
uint256,
bytes memory
) public virtual override returns (bytes4) {
return this.onERC721Received.selector;
}
}
It is throwing the following error:
revert The transaction has been reverted to the initial state. Reason
provided by the contract: "ERC20: transfer amount exceeds balance".
Debug the transaction to get more information.
Probably solution must be like in the following link
https://forum.openzeppelin.com/t/erc20-transferfrom-fails-erc20-transfer-amount-exceeds-balance/16854