Testing payments directly to smart contract address

Question

I've a smart contract with constructor payable type. As per my understanding declaring payable constructor means a smart contract can able to receive a payments. I've published it through metamask on testnet Binance smart chain. But as soon as I go to send funds directly to smart contract address. It appears an error of gas price, with even the smallest amount of transaction i send it doesn't work,

Contract deployed at: https://testnet.bscscan.com/address/0x75d0b70f597fd23e73c5f193af45023bc65471d7

Transaction Failing in: https://testnet.bscscan.com/tx/0x1258efe59c2fd2d074858082d3b20c6742256c231ecbfa9c48eee4d81a73153a Solidity Code:

// SPDX-License-Identifier: Unlicensed
pragma solidity ^0.8.0;
import "hardhat/console.sol";

contract BurgerShop {

    uint256 public cost = 0.2 * (10**18);
    event BurgerBought(address indexed _from, uint256 cost);
    
    constructor() payable{
        emit BurgerBought(msg.sender, cost);
    }

}  

Secondly, I want to know what is the best approach to recieve funds directly send through smart contract address. Like If i have a smart contract A with an address of 0xaaa...zzzz How can user directly deposit into smart contract address from WALLET?

Answer 1

When a constructor uses the payable modifier, the contract is able to accept ETH during deployment. I.e. the deployment transaction can have non-zero value.

But this doesn't mean that the contract is able to accept ETH later.

In order to accept ETH just like an end user address, a contract needs to implement either fallback() or receive() special function.

Docs: https://docs.soliditylang.org/en/v0.8.13/contracts.html#special-functions

Example:

pragma solidity ^0.8;

contract MyContract {
    receive() external payable {
        // executed when the `data` field is empty and `value` is > 0
    }
}