18_Error.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.13;

// An error will undo all changes made to the state during a transaction.

// You can throw an error by calling require, revert or assert.

// require is used to validate inputs and conditions before execution.
// revert is similar to require. See the code below for details.
// assert is used to check for code that should never be false. Failing assertion probably means that there is a bug.

// Use custom error to save gas.

contract Error {

        // Require should be used to validate conditions such as:
        // - inputs
        // - conditions before execution
        // - return values from calls to other functions
    function testRequire(uint _i) public pure {
        require(_i > 10, "Input must be greater than 10");
    }

        // Revert is useful when the condition to check is complex.
        // This code does the exact same thing as the example above
    function testRevert(uint _i) public pure {
        if (_i <= 10) {
            revert("Input must be greater than 10");
        }
    }

        // Assert should only be used to test for internal errors,
        // and to check invariants.

        // Here we assert that num is always equal to 0
        // since it is impossible to update the value of num

    uint public num;

    function testAssert() public view {

        assert(num == 0);
    }

    // custom error
    error InsufficientBalance(uint balance, uint withdrawAmount);

    function testCustomError(uint _withdrawAmount) public view {
        uint bal = address(this).balance;
        if (bal < _withdrawAmount) {
            revert InsufficientBalance({
                balance: bal,
                withdrawAmount: _withdrawAmount
            });
        }
    }
}