Solidity – How to Set msg.value in Function Call Using Ethers.js

ethers.jsfrontendjavascriptsolidity

I've got a function in my smart contract and i want it to take an argument that sets the msg.value and then pays it into the contract:

function deposit(uint256 amount) public payable {
    msg.value = amount
}

I'm trying to make a button on a website that sends a fixed amount into the contract like this:

async function sendTransaction() {
   if (typeof window.ethereum !== 'undefined') {
      await requestAccount()
      const provider = new ethers.providers.Web3Provider(window.ethereum);
      const signer = provider.getSigner();
      const contract = new ethers.Contract(contractAddress, contract.abi, signer);
      const transaction = await contract.deposit()
      await transaction.await()
   }

my question is, is there a way to set the msg.value from within the function its self, so i can call contract.deposit(value), or is there an easier way to set the value using ether.js?

Best Answer

You cannot change msg.value in the contract, it represents the amount of ether sent.

On frontend:

const transaction = await contract.deposit({ value: ethers.utils.parseEther("0.1") })
//sends 0.1 eth
await transaction.wait()

Change the 0.1 to the amount of ether you would like to send.

Related Solutions

Ether Transfer – How to Send Ether to a Contract Successfully

A contract can't forcefully extract ETH from a wallet address, if you want to pay Ether into a contract, you must set the "Value" of the transaction when calling a function (or just send ETH to the contracts address if the fallback function allows it).

Using transfer will transfer from the contract to another address, so with address(this).transfer(msg.value), the contract is just taking the ETH provided by the msg.sender, and passing it to itself.

function sendETHtoContract(uint256 j) public payable {
    //msg.value is the amount of wei that the msg.sender sent with this transaction. 
    //If the transaction doesn't fail, then the contract now has this ETH.
}

Solidity – Implementing Mint and Payable Functions in ERC20 Smart Contracts

You can use something like this:

pragma solidity ^0.8.4;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

contract MyToken is ERC20, Ownable {
    address public creatorAddress = 0xYOUR_ADDRESS;

    constructor() ERC20("MyToken", "MTK") {
        _mint(msg.sender, 10000 * 10 ** decimals());
    }

    function mint(address to, uint256 amount) public payable {
        _mint(to, amount);

        payable(creatorAddress).transfer(msg.value / 10);
    }
}

This code sends 10% of every payment to the creatorAddress.

Best Answer

Related Solutions

Ether Transfer – How to Send Ether to a Contract Successfully

Solidity – Implementing Mint and Payable Functions in ERC20 Smart Contracts

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