Notes

How to send Ether?

You can send Ether to other contracts by:

• transfer (2300 gas, throws error)
• send (2300 gas, returns bool)
• call (forward all gas or set gas, returns bool)

How to receive Ether?

A contract receiving Ether must have at least one of the functions below

• receive() external payable
• fallback() external payable
• receive() is called if msg.data is empty, otherwise fallback() is called.

Which method should you use?

• call in combination with re-entrancy guard is the recommended method to use after December 2019.

Guard against re-entrancy by:

• making all state changes before calling other contracts
• using re-entrancy guard modifier

Code

solidity
SendingEther.sol
Copy
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

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");
   }
}