Incorrect_modifier.md

Incorrect modifier

Function Modifiers:

They can be used to change the behaviour of functions in a declarative way. For example, you can use a modifier to automatically check a condition prior to executing the function. The function’s control flow continues after the _; in the preceding modifier. Multiple modifiers are applied to a function by specifying them in a whitespace-separated list and are evaluated in the order presented. The modifier can choose not to execute the function body at all and in that case the return variables are set to their default values just as if the function had an empty body. The _; symbol can appear in the modifier multiple times.

If a modifier does not execute _; or revert, the function using that modifier will return the default value causing unexpected behavior.

pragma solidity 0.8.10;

contract test {

    // Assume other required functionality is correctly implemented

    mapping (uint256 => address) addresses;
    bool check;

    modifier onlyIf() {
        if (check) {
            _;
        }
    }

    function setAddress(uint id, address addr) public {
        addresses[id] = addr;
    }

    function getAddress(uint id) public onlyIf returns (address) {
        return addresses[id];
    }
}

In above contract if we call getAddress() function it will returns the expected addresses if check is true otherwise it will return zero address (default value) if check is false.

• Note: Be sure to use require(), assert(), and revert() as needed in your logic and to implement strong modifiers with proper reasoning.