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Lesson 18:
Errors
Introduction to errors and how to use it in your smart contracts.
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Errors
Errors in Solidity provide a convenient and gas-efficient way to explain why an operation failed. They can be defined inside and outside of contracts (including interfaces and libraries).
They have to be used together with revert statement which causes all changes in the current call to be reverted and passes the error data back to the caller.
Instances of errors can only be created using revert statements.
Examples of ways to use custom errors:
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;
// Error for insufficient balance for transfer. Needed `required` but only
// `available` available.
// @param available balance available.
// @param required requested amount to transfer.
error InsufficientBalance(uint256 available, uint256 required);
// Error for invalid recipient address
error InvalidRecipient(address recipient);
// Error for transfer amount being zero
error ZeroTransfer();
contract MyToken {
mapping(address => uint) balance;
function transfer(address to, uint256 amount) public {
if (amount > balance[msg.sender]) {
revert InsufficientBalance({
available: balance[msg.sender],
required: amount
});
}
if (to == address(0)) {
revert InvalidRecipient(to);
}
if (amount == 0) {
revert ZeroTransfer();
}
balance[msg.sender] -= amount;
balance[to] += amount;
}
// ...
}