从ERC20调用ERC721函数会引发一个错误

Question

我在ERC721合同内打电话给ERC721 20。我在编译和迁移它时没有问题，但是当执行这一行代码时，元问询会抛出一个错误。

这是我的代码：

导致错误的行: Erc20Contract.transfer(nftInfo从….creator，10)

ERC721

// SPDX-License-Identifier: MIT
pragma solidity ^0.7.0;

import "../openzeppelin-contracts/contracts/token/ERC721/IERC721.sol";
import "../openzeppelin-contracts/contracts/token/ERC721/ERC721.sol";
import "../openzeppelin-contracts/contracts/token/ERC721/IERC721Receiver.sol";
import "../openzeppelin-contracts/contracts/math/SafeMath.sol";
import "../openzeppelin-contracts/contracts/utils/Address.sol";
import "../openzeppelin-contracts/contracts/utils/Counters.sol";
import "./ERC20Token.sol";

contract NFTtoken is ERC721 {
    using SafeMath for uint256;
    using Address for address;
    using Counters for Counters.Counter;
    Counters.Counter private _tokenIds;
    ERC20Token Erc20Contract;

    constructor(address tokenAddress) ERC721("NC NFT example", "NCNFT") {
        owner = msg.sender;
        decimals = 0;
        Erc20Contract = ERC20Token(tokenAddress);
    }
    function transferNFT(address from, address to, uint256 tokenId)  public returns (bool){
        transferFrom(from, to, tokenId);
        Erc20Contract.transfer(nftInfo[from].creator, 10);
        //^^^^^^^^^ this line is causing an errror. 
    }
}

ERC20

// SPDX-License-Identifier: MIT
pragma solidity ^0.7.0;
import "../openzeppelin-contracts/contracts/token/ERC20/IERC20.sol";
import "../openzeppelin-contracts/contracts/math/SafeMath.sol";

contract ERC20Token is IERC20 {
    function transfer(address to, uint256 tokens) public override returns (bool) {
        balances[msg.sender] = SafeMath.sub(balances[msg.sender], tokens);
        balances[to] = SafeMath.sub(balances[to], tokens);
        emit Transfer(msg.sender, to, tokens);
        return true;
    }
}

2_deploy_contracts.js

const NFTtoken = artifacts.require("NFTtoken");
const ERC20token = artifacts.require("ERC20Token")
let _totalSupply = 20000;

module.exports = function(deployer) {
    deployer.deploy(ERC20token, _totalSupply, web3.utils.toWei('0.01', 'ether'), [web3.utils.asciiToHex('Rama'), web3.utils.asciiToHex('Nick'), web3.utils.asciiToHex('Jose')]); 
    deployer.deploy(NFTtoken, ERC20token.address);
};

错误：

MetaMask - RPC Error: [ethjs-query] 
while formatting outputs from RPC 
'{"value":{"code":-32603,"data":{"message":"VM Exception while processing transaction: revert",
"code":-32000,"data": {"0x18abb17dda4df83e94eb19c0db814e9d4d3ec65a5f96001c0597fb9e93f1a816":{"error":"revert","program_counter":4807,"return":"0x"},
"stack":"RuntimeError: VM Exception while processing transacti
on: revert\n    at Function.RuntimeError.fromResults (C:\\Program Files\\WindowsApps\\GanacheUI_2.5.4.0_x64__5dg5pnz03psnj\\app\\resources\\static\\node\\node_modules\\ganache-core\\lib\\utils\\runtimeerror.js:94:13)\n    at BlockchainDouble.processBlock (C:\\Program Files\\WindowsApps\\GanacheUI_2.5.4.0_x64__5dg5pnz03psnj\\app\\resources\\static\\node\\node_modules\\ganache-core\\lib\\blockchain_double.js:627:24)\n    at runMicrotasks (<anonymous>)\n    at processTicksAndRejections (internal/process/task_queues.js:93:5)","name":"RuntimeError"}}}}' {code: -32603, message: `[ethjs-query] while formatting outputs from RPC '{…/task_queues.js:93:5)","name":"RuntimeError"}}}}'`}

Uncaught (in promise) {code: -32603, message: `[ethjs-query] while formatting outputs from RPC '{…/task_queues.js:93:5)","name":"RuntimeError"}}}}'`, 
stack: '{\n  "code": -32603,\n  "message": "[ethjs-query] wh…gaeaoehlefnkodbefgpgknn/background-0.js:1:216902)'}

Answer 1

假设您的NFTtoken有足够的ERC20令牌余额(当您将10个令牌从NFT契约传输到NFT创建者时)，我会说您在ERC20契约上实现的transfer方法是不正确的。

当您将令牌传输到to地址时，您应该将金额add到to余额，而不是减除它：

// SPDX-License-Identifier: MIT
pragma solidity ^0.7.0;
import "../openzeppelin-contracts/contracts/token/ERC20/IERC20.sol";
import "../openzeppelin-contracts/contracts/math/SafeMath.sol";

contract ERC20Token is IERC20 {
    function transfer(address to, uint256 tokens) public override returns (bool) {
        balances[msg.sender] = SafeMath.sub(balances[msg.sender], tokens);
        balances[to] = SafeMath.add(balances[to], tokens);
        emit Transfer(msg.sender, to, tokens);
        return true;
    }
}