Combining Token Approval and Contract Invocation in Ethers.js
When interacting with decentralized applications (dApps) built on top of Ethereum, one common pattern involves transferring tokens to a smart contract. However, this can lead to unnecessary overhead and potential security risks due to the two separate calls required: token approval and contract invocation.
In our current implementation, we make two separate calls:
await token.approve(contractAddress, amount);- Approving a specified amount of tokens for the given contract.
await contract.myFunction();- Invoking the contract's function using the approved tokens.
This approach can be cumbersome and error-prone, as it requires manual management of the approval process and ensures that only specific functions are invoked on the contract.
Introducing a Single Call: Token Approval and Contract Invocation in Ethers.js
To simplify this process and reduce unnecessary overhead, we'll introduce a new method called approveAndInvoke. This function will combine token approval with contract invocation into a single call.
import { ethers } from 'ethers';
/**
* Combines token approval and contract invocation in a single call.
*
* @param {string} tokenAddress - The address of the token to approve.
* @param {string} contractAddress - The address of the smart contract to invoke.
* @param {number} amount - The amount of tokens to approve for the contract.
*/
async function approveAndInvoke(tokenAddress, contractAddress, amount) {
// Get the provider instance
const provider = await ethers.getProvider();
// Approve the token for the given contract
const approveResponse = await provider approves(tokenAddress, contractAddress, amount);
if (!approveResponse) throw new Error('Token approval failed');
// Invoke the contract function using the approved tokens
try {
await provider.invokeStatic(contractAddress, 'myFunction', { tokens: [amount] });
} catch (error) {
console.error(error); // Token approval and invocation failed
}
}
export default approveAndInvoke;
Example Usage
import { approveAndInvoke } from './approveAndInvoke';
// Replace with your token address, contract address, and amount
const tokenAddress = '0x...'; // Replace with the actual token address
const contractAddress = '0x...'; // Replace with the actual contract address
const amount = 10n;
approveAndInvoke(tokenAddress, contractAddress, amount).then(() => {
console.log('Tokens approved and invoked successfully!');
}).catch((error) => {
console.error(error); // Token approval and invocation failed
});
This approveAndInvoke function takes in the required parameters, approves the specified tokens for the given contract, and invokes the contract's function using those approved tokens. This approach reduces the overhead of manual token approval and contract invocation, making it a more convenient and secure way to interact with dApps built on top of Ethereum.