the gas fee will always be native currency, in your case probably you called the native currency TBNB when you added Binance testnet to metamask.
In order to make a transaction with ERC20 tokens sometimes you also need to approve the transfer of those tokens so that a smart contract can transfers the tokens from one address to another address.
Iâve modified the function slightly to run approve before running the swap but to no avail.
const swapToken = async () => {
const web3 = await Moralis.enableWeb3();
// This is the smart contract address
const swapConAdd = process.env.REACT_APP_SWAP_SMART_CON;
try {
let stableAdd; // stablecoin's contract address
const stableSym = fromToken; // stablecoin symbol
const stableDec = fromDec; // stablecoin decimal
const buyerAdd = props.wallAdd; // user wallet address
const buyerAmt = stableVal; // stablecoin value/amount
const sellerAmt = tysVal; // custom token value/amount
if(stableSym.toLowerCase() === "usdt") {
stableAdd = process.env.REACT_APP_USDT_ADD;
}
// Approve user wallet for transaction
const stableAbi = await getStableCoinAbi(stableSym.toLowerCase());
const stableOpt = {
contractAddress: process.env.REACT_APP_USDT_ADD,
functionName: "approve",
abi: stableAbi,
params: {
spender: buyerAdd,
amount: Moralis.Units.Token(buyerAmt.toString(), stableDec.toString())
},
};
const approveStable = await Moralis.executeFunction(stableOpt);
// Approve tys wallet for transaction
const tysAbi = await getStableCoinAbi("xrp"); // testing with xrp
const tysOpt = {
contractAddress: process.env.REACT_APP_TYS_ADD,
functionName: "approve",
abi: tysAbi,
params: {
spender: process.env.REACT_APP_TYS_WALLET,
amount: Moralis.Units.Token(sellerAmt.toString(), "18")
},
};
const approveTys = await Moralis.executeFunction(tysOpt);
const abi = await getSwapAbi();
const swapOpt = {
contractAddress: swapConAdd,
functionName: "swap",
abi: abi,
params: {
buyerToken: stableAdd,
buyer: buyerAdd,
buyerAmt: Moralis.Units.Token(buyerAmt.toString(), stableDec.toString()),
sellerAmt: Moralis.Units.Token(sellerAmt.toString(), "18")
}
};
const swap = await Moralis.executeFunction(swapOpt);
swap.on("error", (error) => {
console.log(error);
})
} catch(error) {
console.log("transfer error", error);
}
}
Approving both erc20 tokens was a success, it was showing the right value, with the right token during Metamask confirmation & I was able to get the blockHash data & etc. back.
But when it run the executeFunction for swap, I got âexecution revertedâ error.
What am I missing here? How do I make this work?
who is buyerAdd, you should approve the smart contract address
@cryptokid buyerAdd is the buyerâs wallet address, which is also the current userâs wallet address, sellerâs wallet address will always be the wallet where we hold our own custom token.
How do you approve a smart contract & which smart contract?
Do you mean calling the approve method for a transfer thatâs in an erc20 tokenâs smart contract?
If itâs the latter then thatâs already been called in âstableOptâ, under âcontractAddressâ :
...
const stableOpt = {
contractAddress: process.env.REACT_APP_USDT_ADD, // USDT SMART CONTRACT ADDRESS
functionName: "approve",
abi: stableAbi,
params: {
spender: buyerAdd,
amount: Moralis.Units.Token(buyerAmt.toString(), stableDec.toString())
},
};
...
I think that on approve, you have to put on spender the address that will transfer that ERC20 token, in your case it may be the smart contract that will do that transfer from one address to another address.
Ok, let me give that a try.
@cryptokid I think you were right, I should have approved the smart contract address instead of wallet addresses as stated in the Metamask confirmation popup.
However, still getting the same âexecution revertedâ error when trying to executeFunction for swap.
What is the usual cause of this error?
sometimes you can see a specific error message in bscscan after you submit the transaction, if it happen for the execution to stop in a require
Yea sorry but thereâs nothing on the testnet BscScan, no swap transactions recorded anywhere, I can only see the approve ones.
I mean the transaction that you are trying to make now, if you submit it, probably it will fail, but it could also show an error message
Yes, this is all that it is saying, same as before, which doesnât really say much.
I mean, after you make that transaction with MetaMask, you can see the transaction that failed in bscscan and see there if there is additional info for the error.
There is literally NOTHING.
This is the latest transaction in Metamask
These are the latest transactions recorded on BscScan.
This is the last recorded bep-20 token transaction.
Like I said, I only see transactions for approve but not swap.
Then maybe you didnât execute that swap, it should be there as a failed transaction.
Hereâs the smart contract for swap:
pragma solidity ^0.8.10;
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/release-v4.4/contracts/token/ERC20/IERC20.sol";
contract TokenSwap {
IERC20 public buyerToken;
address public buyer;
uint public buyerAmt;
IERC20 public sellerToken;
address public seller;
uint public sellerAmt;
constructor(
address _buyerToken,
address _buyer,
uint _buyerAmt,
uint _sellerAmt
) {
buyerToken = IERC20(_buyerToken);
buyer = _buyer;
buyerAmt = _buyerAmt;
sellerToken = IERC20(<<custom token contract address>>);
seller = <<wallet address that holds our custom token>>;
sellerAmt = _sellerAmt;
}
function swap() public {
require(msg.sender == buyer || msg.sender == seller, "Not authorized");
require(
buyerToken.allowance(buyer, address(this)) >= buyerAmt,
"Token 1 allowance too low"
);
require(
sellerToken.allowance(seller, address(this)) >= sellerAmt,
"Token 2 allowance too low"
);
_safeTransferFrom(buyerToken, buyer, seller, buyerAmt);
_safeTransferFrom(sellerToken, seller, buyer, sellerAmt);
}
function _safeTransferFrom(
IERC20 token,
address sender,
address recipient,
uint amount
) private {
bool sent = token.transferFrom(sender, recipient, amount);
require(sent, "Token transfer failed");
}
}
This is how swap function was executed:
...
const abi = await getSwapAbi();
const swapOpt = {
contractAddress: swapConAdd, // swap contract address
functionName: "swap",
abi: abi,
params: {
buyerToken: stableAdd, // stablecoin contract address
buyer: buyerAdd, // buyer's wallet address
buyerAmt: Moralis.Units.Token(buyerAmt.toString(), stableDec.toString()), // value of how much buyer has to transfer
sellerAmt: Moralis.Units.Token(sellerAmt.toString(), "18") // value of how much seller has to transfer
}
};
const swap = await Moralis.executeFunction(swapOpt);
swap.on("error", (error) => {
console.log(error);
})
...
This is the ABI for swap:
const abi = [
{
constant: true,
inputs: [
{
internalType: "address",
name: "buyerToken",
type: "address"
},
{
internalType: "address",
name: "buyer",
type: "address"
},
{
internalType: "uint256",
name: "buyerAmt",
type: "uint256"
},
{
internalType: "uint256",
name: "sellerAmt",
type: "uint256"
}
],
name: "swap",
outputs: [
{
internalType: "uint256",
name: "",
type: "uint256"
}
],
payable: true,
stateMutability: "view",
type: "function"
}
];
Now, just looking at these, can you see anything & tell me how swap was not executed correctly?
it looks like there are 2 transfers here, that means that it will require two approves
Yes, 2 transfers. I did approve both, even though it mightâve been the wrong approach.
...
// Approve user wallet for transaction
const stableAbi = await getStableCoinAbi(stableSym.toLowerCase());
const stableOpt = {
contractAddress: process.env.REACT_APP_USDT_ADD,
functionName: "approve",
abi: stableAbi,
params: {
spender: buyerAdd,
amount: Moralis.Units.Token(buyerAmt.toString(), stableDec.toString())
},
};
const approveStable = await Moralis.executeFunction(stableOpt);
// Approve custom token wallet for transaction
const tysAbi = await getStableCoinAbi("xrp"); // testing with xrp
const tysOpt = {
contractAddress: process.env.REACT_APP_TYS_ADD,
functionName: "approve",
abi: tysAbi,
params: {
spender: process.env.REACT_APP_TYS_WALLET,
amount: Moralis.Units.Token(sellerAmt.toString(), "18")
},
};
const approveTys = await Moralis.executeFunction(tysOpt);
...
Can I transfer out from our custom token wallet without having to approve? Since our goal is to make the swap automatic every time a user is trying to buy our custom token.
Ok so, weâre making some progress here, all I did was changing a line in the ABI.
From this :
stateMutability: "view"
To this :
stateMutability: "payable"
And now I got this little warning during the Metamask confirmation popup :
When it fails, I can finally see a transaction recorded on BscScan.
Let me try to see if I can find anything from the BscScan transaction.
No luck, even debug trace is not very helpful or descriptive about the error.
{
"type": "CALL",
"from": "0x04f...c19", // user wallet address
"to": "0xa65...ac78", // smart contract address
"value": "0x0",
"gas": "0x1b28968",
"gasUsed": "0xcb",
"input": "0xfe029156000000000000000000000000337610d27c682e347c9cd60bd4b3b107c9d34ddd00000000000000000000000004fc654d2e22ef7243eb3cbc53d8aaf3fd25bc1900000000000000000000000000000000000000000000000012bc29d8eec7000000000000000000000000000000000000000000000000000029a2241af62c0000",
"error": "execution reverted",
"time": "0s"
}
Hereâs the transaction.
now it could be related to those approves
strange that you had to change that abi, didnât you copy the abi from the contract compilation?