Deleting values from a struct

Question

how do i go about removing values from inside a struct and or a mapping. For example iam creating a smart contract that acts kind of like a vault, iam not yet finished but i have a create an account feature.I would like to add a delete an account feature aswell, i thought about just changing the values inside the struct but there bust be a better way. Here is some of my code:

// Global variables
uint256 uniqueId;

// Account details storage
struct AccDetails {
    string accNickName;
    uint256 creationTimeStamp;
}
mapping(address => AccDetails) public accDetails;

mapping(address => uint256) public balanceOf;
mapping(address => uint256) addrTouniqueIdentifier;
mapping(uint256 => address) uniqueIdentifierToAddr;

// Variables set on contract deployment
constructor() {
    uniqueId = 1;
}


function createAccount(string memory _accNickName) public {
    if(accDetails[msg.sender].creationTimeStamp == 0) {
        accDetails[msg.sender] = AccDetails(_accNickName, block.timestamp);
        addrTouniqueIdentifier[msg.sender] = uniqueId;
        uniqueIdentifierToAddr[uniqueId] = msg.sender;

        emit accountCreated(msg.sender,_accNickName, block.timestamp);

        uniqueId = uniqueId.add(1);
    }else {
        revert("You already have an account created.");
    }
}

Answer 1

Not sure if this is the best way but for me this works,

function deleteAccount() public {
    require(accDetails[msg.sender].creationTimeStamp != 0, "You do not have an account.");
    if(balanceOf[msg.sender] > 0) {
        uint256 _amount = balanceOf[msg.sender];
        balanceOf[msg.sender] = 0;
        payable(msg.sender).transfer(_amount);

        emit withdrawalComplete(msg.sender, accDetails[msg.sender].accNickName, _amount, balanceOf[msg.sender].add(_amount), balanceOf[msg.sender]);
    }
    uint256 _oldUniqueIdentifier = addrTouniqueIdentifier[msg.sender];

    accDetails[msg.sender] = AccDetails("", 0);
    uniqueIdentifierToAddr[addrTouniqueIdentifier[msg.sender]] = address(0);
    addrTouniqueIdentifier[msg.sender] = 0;

    emit accountDeleted(msg.sender, _oldUniqueIdentifier, block.timestamp);
}

Answer 2

Based on your code, deleteAccount will look something like this:

function deleteAccount(address _addr) public {
        delete accDetails[_addr];
        delete balanceOf[_addr];
        delete addrTouniqueIdentifier[_addr];
        delete uniqueIdentifierToAddr[/*balance of the deleted acc*/];
    }

You will have to transfer the deleted account's balance to another address:

function send(address payable _to) public payable {
        (bool sent, bytes memory data) = _to.call{value: msg.value}("");
        require(sent, "Failed to send Ether");
    }

Putting everything together:

function send(address payable _to) public payable {
        (bool sent, bytes memory data) = _to.call{value: msg.value}("");
        require(sent, "Failed to send Ether");
    }

    function deleteAccount(address _addr) public {
        send(payable(to));
        // Reset the value to the default value.
        delete accDetails[_addr];
        delete balanceOf[_addr];
        delete addrTouniqueIdentifier[_addr];
        delete uniqueIdentifierToAddr[/*balance of the deleted acc*/];
    }

Also:

• Consider adding re-entrancy guard to the send function.
• Add events.