Managing values in a mapping

Question

I am creating a simple application that allows a user to set an account address as a string and return it. Part of the criteria is that each name should be unique. A user should be able to change their string if they wish. So far I have the following, which works well as far as I can see;

pragma solidity ^0.8.7;

contract Test {
    mapping(string=>address) _names;
    mapping(address=>string) _addresses;
    
    function setName(string memory name) external {
        require(_names[name]==address(0), "Duplicate name");
        
        _names[name] = msg.sender;
        _addresses[msg.sender] = name;
    }
    
    function readName() external view returns (string memory) {
        return _addresses[msg.sender];
    }
}

The problem I have is that when a user changes their account string, it does not allow the previously set string to be reused by another account (or the same account for that matter). Do I need to remove the previous string values from the mapping in order to reuse account names?

Answer 1

Yes. Try

    function setName(string memory name) external {
        require(_names[name]==address(0), "Duplicate name");

        _names[_addresses[msg.sender]] = address(0);

        _names[name] = msg.sender;
        _addresses[msg.sender] = name;
    }