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getApprovalForTransaction

When dealing with transactions that involve ERC20 tokens (Airdropping ERC20, buy NFTs with ERC20, etc.) you often have to do a pre-check to see if the targeted contract has the sufficient allowance to "take" the ERC20 tokens from the caller's wallet.

This extension is a handy method that checks for the allowance and requests to approve for more if current allowance is insufficient

Example

import { getApprovalForTransaction } from "thirdweb/extensions/erc20";
import { sendAndConfirmTransaction } from "thirdweb";
 
async function buyNFT() {
  const buyTransaction = ... // could be a marketplacev3's buyFromListing
 
  // Check if you need to approve spending for the involved ERC20 contract
  const approveTx = await getApprovalForTransaction({
    transaction: buyTransaction,
    account, // the connected account
  });
  if (approveTx) {
    await sendAndConfirmTransaction({
      transaction: approveTx,
      account,
    })
  }
  // Once approved, you can finally perform the buy transaction
  await sendAndConfirmTransaction({
    transaction: buyTransaction,
    account,
  });
}

Parameters

Returns

a PreparedTransaction