ERC20代币转移到智能合约

Question

嗨，我已经编写了一个简单的智能合约，将erc20令牌从用户转移到智能合约，并从智能合约转移到用户。我在调用transferFrom函数之前批准了它，但事务失败。我试过只打电话给approve，而不打电话给transferFrom。它很管用。我正在林克比测试网上测试。

// SPDX-License-Identifier: MIT
pragma solidity =0.7.6;
pragma abicoder v2;

interface IERC20 {
    function totalSupply() external view returns (uint256);
    function balanceOf(address account) external view returns (uint256);
    function allowance(address owner, address spender) external view returns (uint256);
    function transfer(address recipient, uint256 amount) external returns (bool);
    function approve(address spender, uint256 amount) external returns (bool);
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);

}

contract transferToContract {
    address public _WETH = 0x1f9840a85d5aF5bf1D1762F925BDADdC4201F984;
    IERC20 public WETH = IERC20(_WETH);

    function transferToC (uint amount) public
    {
        WETH.approve(msg.sender,amount);
        WETH.transferFrom(msg.sender,address(this),amount);
    }
    
    function transferFromC(uint amount) public{
        WETH.approve(address(this),amount);
        WETH.transferFrom(address(this),msg.sender,amount);
    }
    
    function getbal() public view returns(uint){
        return WETH.balanceOf(msg.sender);
    }
    
    
}

我在测试注入了web3的混音。我得到的错误是

Gas estimation errored with the following message (see below). The transaction execution will likely fail. Do you want to force sending?
execution reverted: Uni::transferFrom: transfer amount exceeds spender allowance { "originalError": { "code": 3, "data": "0x08c379a00000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000003c556e693a3a7472616e7366657246726f6d3a207472616e7366657220616d6f756e742065786365656473207370656e64657220616c6c6f77616e636500000000", "message": "execution reverted: Uni::transferFrom: transfer amount exceeds spender allowance" } }

此外，我在 rinkeby 测试网上的测试钱包中有令牌，我正在使用注入的 remix web3 进行部署。

Answer 1

我希望我的合同接受来自外部帐户的令牌，这些令牌很少(可以是任何令牌，但基于ERC20)。因此，要直接调用approve函数，我需要创建令牌契约的实例，那么我如何使用web3创建实例呢？

任何代码段都会有帮助，如果您可以共享指向任何文档的链接，同样也会有帮助。

Answer 2

WETH.approve(msg.sender,amount);

此行批准用户使用合同的令牌。反之亦然。

如果您希望批准合同以操作用户的令牌，用户需要直接在WETH合同上执行< code > approve(yourcontracaddress，amount)(不通过您的合同)。

我在另一个答案中也提到了类似的话题。TLDR部分也与您的问题相关：https://stackoverflow.com/a/67642090/1693192