call transferFrom function by using ethers, getting error ERC20: insufficient allowance

[Sha777wee]

Hi everyone.

I had called the approve function and changed the account,but i still get the error:insufficient allowance.I confirm the account had sufficient allowance.The strange thing is that sometimes it can be called normally, most of the time it will throw this error directly.

Error:

extract error Error: execution reverted: "insufficent allowance" (action="estimateGas", data="0x08c379a000000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000015696e737566666963656e7420616c6c6f77616e63650000000000000000000000", reason="insufficent allowance", transaction={ "data": "0x23b872dd000000000000000000000000f39fd6e51aad88f6f4ce6ab8827279cfffb9226600000000000000000000000070997970c51812dc3a010c7d01b50e0d17dc79c80000000000000000000000000000000000000000000000000000000000000064", "from": "0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266", "to": "0x5FbDB2315678afecb367f032d93F642f64180aa3" }, invocation=null, revert={ "args": [ "insufficent allowance" ], "name": "Error", "signature": "Error(string)" }, code=CALL_EXCEPTION, version=6.3.0)
    at makeError (errors.ts:663:1)
    at getBuiltinCallException (abi-coder.ts:118:1)
    at AbiCoder.getBuiltinCallException (abi-coder.ts:229:1)
    at BrowserProvider.getRpcError (provider-jsonrpc.ts:808:1)
    at BrowserProvider.getRpcError (provider-browser.ts:88:1)
    at provider-jsonrpc.ts:423:1

Environment:

• hardhat@2.13.1

• metask@10.28.3

Contract:

contract SWC {
    string public name = "SW Coin";
    string public symbol = "SWC";
    uint8 public decimals = 18;
    uint public totalSupply = 1000;
    mapping(address => uint) public balanceOf;
    mapping(address => mapping(address => uint)) public allowance;

    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(
        address indexed _owner,
        address indexed _spender,
        uint256 _value
    );

    constructor() {
        balanceOf[msg.sender] = totalSupply;
    }

    function mint(address receiver) public returns (bool success) {
        require(balanceOf[receiver] + 100 > balanceOf[receiver]);
        require(totalSupply + 100 > totalSupply);
        balanceOf[receiver] += 100;
        totalSupply += 100;
        return true;
    }

    function transfer(
        address _to,
        uint256 _value
    ) public returns (bool success) {
        require(balanceOf[msg.sender] >= _value, "insufficent balnace");
        balanceOf[msg.sender] -= _value;
        balanceOf[_to] += _value;
        emit Transfer(msg.sender, _to, _value);
        return true;
    }

    function approve(
        address _spender,
        uint256 _value
    ) public returns (bool success) {
        require(balanceOf[msg.sender] >= _value, "insufficent balnace");
        allowance[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    function transferFrom(
        address _from,
        address _to,
        uint256 _value
    ) public returns (bool success) {
        require(
            allowance[_from][msg.sender] >= _value,
            "insufficent allowance"
        );
        require(balanceOf[_from] >= _value, "insufficent balnace");
        allowance[_from][msg.sender] -= _value;
        balanceOf[_from] -= _value;
        balanceOf[_to] += _value;
        emit Transfer(_from, _to, _value);
        return true;
    }

    fallback() external {}
}

ethres code:

const provider = new ethers.BrowserProvider(window.ethereum);

const contract = new ethers.Contract(address,abi,await provider.getSigner() );

const from = addressExtractFromRef.current.input.value;

const to = addressExtractToRef.current.input.value;

const amount = amountToExtractREf.current.input.value;

const result = await contract.transferFrom(from, to, amount);

[zemse]

I had called the approve function

Which network are you using?

If this is a local hardhat network, then if you restart it then you lose the allowance and have to re-approve.

If this is a live network, then how long are you waiting it's possible that when you are estimating gas, the block containing the thx is no yet received on the node which you are using.

It can be better to just approve on the fly if it is needed, e.g.

const allowance = await contract.allowance(ownerAddress, spenderAddress);
if(allowance.lt(amount)) {
    const approveTx = await contract.connect(ownerSigner).approve(spender, amount); // this tx should go through owner account
    await approveTx.wait(); // wait for tx to confirm
}

// transfer now since allowance exists now
const transferTx = await contract.transferFrom(from, to, amount); // this tx should go through spender account

[Sha777wee]

I using it in a local hardhat network and didn't not restart the network. I can check the allowance by calling the allowance(from,to) that it is equail to 100. But when I call the transfer(from,to,100), it says "insufficent allowance".

[zemse]

Note that allowance needs to be present for allowance(from,spender) (not to) where spender is the account that calls the ERC20 contract.

[Sha777wee]

My fault,there's something wrong with my description. In fact，I use the same addresss for to and spender.