Ethereum: Web3 Contract (React) – SafeERC20 low-level call with ERC20 token (USDT) failed
As a developer working on a smart contract or web3 application, you are probably familiar with the concept of interacting with different blockchain networks. In this article, we will explore an issue reported by several users and developers.
The Problem
The issue is related to the SafeERC20 low-level call mechanism in Ethereum’s Web3 API. Specifically, if you are using an Ethereum-based contract (like Etherscan), attempting to call a function with an ERC20 token (like USDT) will trigger an error.
The Symptoms
The symptoms are as follows:
- The smart contract works fine when you try to use it with ETH (Ethereum).
- However, if you use the same contract with an ERC20 token such as USDT, you will run into problems.
- The error message usually indicates that the call failed, but does not provide any specific details.
The solution
To fix this problem, you have a few options:
- Use a different token
: Instead of using the ERC20 token (USDT), try using a different token supported by Ethereum, such as DAI or LINK.
- Implement a fallback mechanism: You can implement a fallback mechanism in your contract that will attempt to call the function with an ERC20 token before falling back to ETH if necessary.
Code Example
Here is an example code snippet in Solidity (the programming language used for Ethereum smart contracts) that shows how you could implement a fallback mechanism:
pragma solidity ^0.8.0;
contract SafeERC20Fallback {
function callFunction() public {
// First try calling the function with ETH
if (msg.sender.balance > 10 10*18) {
// If successful, return the value of the variable
uint256 result = msg.value / 10 ** 18;
return result;
}
// If unsuccessful, try calling the function with an ERC20 token
address[] memory tokens = [address(0x89f8C7CE9e77fBC2a3Bc6BB5dA1bF6Cc4bfc94ce)];
for (uint256 i = 0; i < tokens.length; i++) {
// Get the token contract
token contract = Token(address(tokens[i]));
// Try calling the function with the token
uint256 result = contract.callFunction();
// If successful, return the value of the variable
if (result > 0) {
return result;
}
}
// If both methods fail, roll back the transaction
revert();
}
}
struct Token {
address public tokenAddress;
}
Conclusion
In this article, we investigated an issue reported by several users and developers related to failed low-level calls to SafeERC20 with ERC20 tokens when using Ethereum. We also provided a code sample in Solidity that shows how to implement a fallback mechanism for such cases.
By understanding the cause of the problem and implementing an appropriate solution, you should be able to resolve these issues and move on with developing your smart contract or Web3 application.