msg.value vs ERC-20 Solidity Examples

Ethereum Example

This example uses msg.value the native token of a network

/// SPDX-License-Identifier: MIT
pragma solidity ^0.8.9;

contract Game {	
	function startGame() external payable {
        (bool sent, bytes memory data) = payable(address(this)).call{value: msg.value}("");
        require(sent, "Failed to send Ether");
    }
}

ERC-20 Example

This example uses an ERC-20 token which can vary network by network.
This example also uses Open Zeppelin for the ERC-20 standard.

/// SPDX-License-Identifier: MIT
pragma solidity ^0.8.9;


import “@openzeppelin/contracts/token/ERC20/IERC20.sol”;

contract Game {
	
	IERC20 token;

	constructor(address token) {
		token = IERC20(token);
    }
    
	function startGame() external {
        (bool succes, ) = token.transferFrom(msg.sender, payable(address(this)), 1 ether);
        
        require(success, "Failed To Transfer");
    }
}

SafeERC20 Utility

This is an extension on the above example that handles the error catching/throwing for you on failed transfers.

/// SPDX-License-Identifier: MIT
pragma solidity ^0.8.9;

import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import “@openzeppelin/contracts/token/ERC20/IERC20.sol”;

contract Game {
    
    using SafeERC20 for IERC20;
    
	IERC20 token;

	constructor(address token) {
		token = IERC20(token);
    }
    
    /**
     * SafeERC20 handles throwing an error for you
     */
	function startGame() external {
		token.safeTransferFrom(msg.sender, payable(address(this)), 1 ether);
    }
}