ethereum solidity what's the difference between require and revert + error - ethereum

Question

I'm wondering what's the difference from
contract TestToken {
mapping(address => uint) balance;
error InsufficientBalance(uint256 available, uint256 required);
function transfer(address to, uint256 amount) public {
if (amount > balance[msg.sender])
// Error call using named parameters. Equivalent to
// revert InsufficientBalance(balance[msg.sender], amount);
revert InsufficientBalance({
available: balance[msg.sender],
required: amount
});
balance[msg.sender] -= amount;
balance[to] += amount;
}
// ...
}
and
contract TestToken {
mapping(address => uint) balance;
error InsufficientBalance(uint256 available, uint256 required);
function transfer(address to, uint256 amount) public {
require(balance[msg.sender]<amount, "Insufficient Balance");
balance[msg.sender] -= amount;
balance[to] += amount;
}
// ...
}
to handle error in solidity

Answer 1

From the low-level standpoint, both approaches are the same. Both throw an exception with an array of bytes as the exception data.
You can catch both errors in the low-level catch (bytes memory) block
function foo() public {
try this.transfer(address(0x123), 2) {
// ok
} catch (bytes memory data) {
// returns either the encoded object or the encoded string
}
}
But you can only catch the string-encoded error with the "regular" catch Error(string memory) block
function foo() public {
try this.transfer(address(0x123), 2) {
// ok
} catch Error (string memory reason) {
// returns the string message
// fails to catch if an object is returned
}
}
Docs: https://docs.soliditylang.org/en/v0.8.13/control-structures.html#try-catch
Note that there is a logical error in the second snippet.
// `balance` needs to be lower than `amount`
// otherwise fail
require(balance[msg.sender]<amount, "Insufficient Balance");
should be
// `balance` needs to be larger or equal than `amount`
// otherwise fail
require(balance[msg.sender] => amount, "Insufficient Balance");

Answer 2

In require we specify a condition that, if false, it will revert.
Revert and error is more sophisticated version of the require, where you can specify the condition to depend on the context and create a custom error.
For example
error InvalidAmount (uint256 sent, uint256 minRequired);
contract TestToken {
mapping(address => uint) balances;
uint minRequired;
constructor (uint256 _minRequired) {
minRequired = _minRequired;
}
function list() public payable {
uint256 amount = msg.value;
if (amount < minRequired) {
revert InvalidAmount({
sent: amount,
minRequired: minRequired
});
}
balances[msg.sender] += amount;
}
}
In that code an error called "Invalid amount" is required and it is made to depend on the minimum amount fed in to the constructor. If amount is less than minimum amount, transaction will revert with the custom error which will specify the amount fed by the user and the minimum amount fed in to constructor.