# Solidity: Transfer Ether Safely Today

**Published by:** [backdoor](https://paragraph.com/@backdoor705/)
**Published on:** 2022-09-18
**URL:** https://paragraph.com/@backdoor705/solidity-transfer-ether-safely-today

## Content

Solidity: Transfer Ether Safely TodayFrom https://solidity-by-example.org/sending-ether/3 ways to send Ether:2 ways to receive Ether: A contract receiving Ether must have at least one of the functions belowreceive() external payablefallback() external payablereceive() is called if msg.data is empty, otherwise fallback() is called.// SPDX-License-Identifier: MIT pragma solidity ^0.8.13; contract ReceiveEther { /* Which function is called, fallback() or receive()? send Ether | msg.data is empty? / \ yes no / \ receive() exists? fallback() / \ yes no / \ receive() fallback() */ // Function to receive Ether. msg.data must be empty receive() external payable {} // Fallback function is called when msg.data is not empty fallback() external payable {} function getBalance() public view returns (uint) { return address(this).balance; } } contract SendEther { function sendViaTransfer(address payable _to) public payable { // This function is no longer recommended for sending Ether. _to.transfer(msg.value); } function sendViaSend(address payable _to) public payable { // Send returns a boolean value indicating success or failure. // This function is not recommended for sending Ether. bool sent = _to.send(msg.value); require(sent, "Failed to send Ether"); } function sendViaCall(address payable _to) public payable { // Call returns a boolean value indicating success or failure. // This is the current recommended method to use. (bool sent, bytes memory data) = _to.call{value: msg.value}(""); require(sent, "Failed to send Ether"); } } Recommend ways for call.valueUse call.value + patterns that eliminate reentrancy https://consensys.net/diligence/blog/2019/09/stop-using-soliditys-transfer-now/Checks-Effects-Interactions Patternperform some checks (who called the function, are the arguments in range, did they send enough Ether, does the person have tokens, etc.)effects to the state variables of the current contract should be made.Interaction with other contracts should be the very last step in any function.make sure that all your interactions (external calls) happen at the end.contract Fixed { ... function withdraw() external { // 1. Checks require(balanceOf[msg.sender] > 0); // 2. Effects uint256 amount = balanceOf[msg.sender]; balanceOf[msg.sender] = 0; // 3. Interactions (bool success, ) = msg.sender.call.value(amount)(""); require(success, "Transfer failed."); } } Use a Reentrancy Guardcontract Guarded { ... bool locked = false; function withdraw() external { require(!locked, "Reentrant call detected!"); locked = true; ... locked = false; } } ReentrancyGuard by OpenZeppelinhttps://docs.openzeppelin.com/contracts/4.x/api/security#ReentrancyGuard https://blog.openzeppelin.com/reentrancy-after-istanbul/

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