ERC20：转账金额超过限额 带有巧克力蛋糕和 NFT 的智能合约

Question

Hello there I have two smart contracts, one is an ERC1155 contract which mints a NFT from Moralis IPFS server, the other is a ERC20 token. I want users to be able to pay for the minted NFT using the ERC20 token but I'm receiving an error on the transferfrom() function: brownie.exceptions.VirtualMachineError: revert: ERC20: transfer amount exceeds allowance. I did some research but nothing helped so far.

This is my ERC1155 contract

import "@openzeppelin/contracts/token/ERC1155/ERC1155.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
// import "@openzeppelin/contracts/utils/math/SafeMath.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@chainlink/contracts/src/v0.8/VRFConsumerBase.sol";

contract NFTPomoBots is ERC1155, Ownable {
    IERC20 private _roboToken;

    constructor(IERC20 roboToken)
        ERC1155(
            "ipfs://QmcPjTnt33BRM5TPGyno7restoftheurl/({id}.json"
        )
    {
        _roboToken = roboToken;
    }

    function mintPomoBot(
        address account,
        uint256 id,
        uint256 amount
    ) public {
        require(_roboToken.transferFrom(msg.sender, address(this), 1));
        _mint(account, id, amount, "");
    }
}

this is the ERC20 contract

// SPDX-License-Identifier: MIT

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/token/ERC20/extensions/ERC20Burnable.sol";

pragma solidity ^0.8.0;

contract RoboToken is ERC20, Ownable {
    uint256 public maxSupply = 100000 * 10**18;

    constructor() ERC20("Pomobots Token", "POMO") {
        _mint(msg.sender, maxSupply);
    }

    function transferToAccount(
        address to,
        uint256 amount,
        bool completedTime
    ) public onlyOwner {
        require(completedTime == true);
        _mint(to, amount);
    }

    function approveNFTContract(address _tokenAddress) public onlyOwner {
        approve(_tokenAddress, maxSupply);
    }
}

this is the test script

def test_can_mint_new_nft():

    # Arrange
    account1 = get_account()
    print(f"account 1 {account1.address}")
    account2 = get_account(1)
    print(f"account 2 {account2.address}")

    robo_token = deploy_erc20_token()
    pomobot_token = NFTPomoBots.deploy(robo_token, {"from": account1})
    # Act
    tx1 = robo_token.transferToAccount(account2, 10, True)
    tx1.wait(1)

    print(robo_token.balanceOf(account2.address))
    tx2 = robo_token.approve(account2.address, robo_token.balanceOf(account2.address))
    tx2.wait(1)

    # assert
    assert pomobot_token.mintPomoBot(account2.address, 20, 1, {"from": account2})
    print(f"nft minted to {account2.address}")
    print(robo_token.balanceOf(account2.address))

Any help is appreciated, also should I make the function minPomobot() payable?

Answer 1

Before calling mintPomoBot function, with the same account ( msg.sender ) you need to call approve(spender, amount) function on RoboToken smart contract where spender = NFTPomoBots' address and amount = 1