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I'm trying to perform approve and transfer under one tx but I don't understand which contract should be calling the approveAndTransferFrom function? Say contract A is trying to transfer tokens to contract B, so should contract A call the function? I also referred to this but it doesn't say also.

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";


contract TokenTransferContract {
    // Reference to the ERC-20 token contract
    IERC20 private token;


// Event to log successful transfer
event TransferApprovedAndExecuted(address indexed from, address indexed to, uint256 amount);

// Constructor to set the ERC-20 token contract address
constructor(address _tokenAddress) {
    token = IERC20(_tokenAddress);
}

// Function to approve and transfer tokens in a single transaction
function approveAndTransferFrom(address _spender, address _to, uint256 _amount) external {
    // Approve the spender to spend tokens on behalf of the contract
    token.approve(_spender, _amount);

    // Transfer tokens from the contract to the specified address
    token.transferFrom(address(this), _to, _amount);

    // Emit an event to log the successful transfer
    emit TransferApprovedAndExecuted(address(this), _to, _amount);
}



}
ratib90486
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1 Answers1

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As only the owner of the tokens can approve the spending of their tokens, yes it should be Contract A that call the approveAndTransferFrom function, with the spender being the TokenTransferContract contract.

However it seems like a bad idea because it would results in the same result as if Contract A simply transferred the tokens directly to Contract B but with higher gas cost.

If your goal is do both operations in a single transaction, you might want to check out this thread: Is it possible to make approve and transferfrom in single transaction?

Pacdac
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