如何从 javascript 文件中批准 ERC20 代币的支出？

Question

我有两个合约 ERC20 和 ERC721。 每次调用 erc721 transferFrom function 时，我想向 ERC721 的创建者（铸币者）发送一些 erc20 代币。

经过一番研究，我发现我必须做两件事。

1. 调用 ERC20.transferfrom 在 ERC721 transferFrom function
2. 从前端批准 erc20 代币的支出

似乎第二个给我带来了一些问题。 请在下面查看我的代码：非常感谢您的帮助。

++ 我也不确定我是否从 ERC721 合约中正确调用 ERC20.transferFrom。 这是正确的方法吗？

ERC721合约：

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 {
.
.
.
    ERC20Token Erc20Contract;

    constructor(address tokenAddress) ERC721("NC NFT example", "NCNFT") {
        owner = msg.sender;
        decimals = 0;
        Erc20Contract = ERC20Token(tokenAddress);
    }
function mint(string calldata nftName) external payable {
        uint256 newItemId = _tokenIds.current();
        _mint(msg.sender, newItemId);

        nftInfo[msg.sender].name = nftName;
        nftInfo[msg.sender].creator = msg.sender;

        allValidTokenIndex[newItemId] = allValidTokenIds.length;
        allValidTokenIds.push(newItemId);
        _tokenIds.increment();
    }
    function transferNFT(address from, address to, uint256 tokenId)  public returns (bool){
        transferFrom(from, to, tokenId);
        Erc20Contract.transferFrom(to, nftInfo[from].creator, 10);
    }
}
.
.
.

应用程序.js

transferNFT: function() {
  NFTContract.deployed().then(function(contractInstance) {
    let toAddress = $("#to-address").val();
    //    function transferFrom(address _from, address _to, uint256 _tokenId) public payable {
    let NFTid_temp = $("#nft-id").val();
    let NFTid = NFTid_temp.substring(7);
    console.log("to = " + toAddress);
    console.log("nftid = " + NFTid);
    Voting.deployed().then(function(votingcontractInstance) { votingcontractInstance.approve(contractInstance.address, votingcontractInstance.balanceOf(web3.eth.accounts[1]))});
    contractInstance.transferNFT(web3.currentProvider.selectedAddress, toAddress, NFTid, {gas: 140000, from: web3.eth.accounts[0]});
  })
}

错误信息

app.js:10169 Uncaught (in promise) BigNumber Error: new BigNumber() not a number: [object Object]
    at raise (http://localhost:8080/app.js:10169:25)
    at http://localhost:8080/app.js:10157:33
    at new BigNumber (http://localhost:8080/app.js:9184:67)
    at new BigNumber (http://localhost:8080/app.js:9194:25)
    at toBigNumber (http://localhost:8080/app.js:2084:12)
    at Object.toTwosComplement (http://localhost:8080/app.js:2095:21)
    at SolidityTypeAddress.formatInputInt [as _inputFormatter] (http://localhost:8080/app.js:2995:38)
    at SolidityTypeAddress.SolidityType.encode (http://localhost:8080/app.js:3648:17)
    at http://localhost:8080/app.js:15577:29
    at Array.map (<anonymous>)

Answer 1

我怀疑这条线：

votingcontractInstance.balanceOf(web3.eth.accounts[1]))

你能检查它的类型吗？ 我认为它返回“字符串”，但它必须是数字。 如果它是字符串，要么用Number包装它

 Number(votingcontractInstance.balanceOf(web3.eth.accounts[1])))

或者使用web3.utils.toBN()

  web3.utils.toBN(votingcontractInstance.balanceOf(web3.eth.accounts[1])))