Update struct when NFT is transferred

Smart Contracts
1

Is that possible?

My ERC721 is saving the "author" of the NFT, but I would like to change this to "holder" - This ofcause if quite easy, but I would like to have the NFT struct updated whenever the NFT changes wallet, in order to always make sure that the "holder" is the current and not the original minter

2

hey @Kion_Larsen
to do this you only have to update the struct at any transfer. If you can share the code I can help more

3

Hi

Well the struct looks like this:

struct Lip {
    string name;
    uint256 id;
    uint256 dna;
    uint16 level;
    uint8 rarity;
    address payable holder;
  }

And the mint function is like this:

function _createLip(string memory _name) internal {
    uint8 randRarity = uint8(_createRandomNum(100));
    uint256 randDna = _createRandomNum(10**16);
    Lip memory newLip = Lip(_name, COUNTER, randDna, 1, randRarity, payable(msg.sender));
    lips.push(newLip);
    _safeMint(msg.sender, COUNTER);
    emit NewLip(msg.sender, COUNTER, randDna);
    COUNTER++;
  }

I do not know exactly what you are looking for, but if you have an idea on how I can update the struct when transfer is completed OR maybe a solution on how I can update the struck manually, I'd be happy too :slight_smile:

Basically you should forget about the code, because this is just the inspiration, and update of the level can be done like this:

  function levelUp(uint256 _lipId) public payable {
    require(msg.value >= fee);
    require(ownerOf(_lipId) == msg.sender, "You are not owner");
    Lip storage lip = lips[_lipId];
    lip.level++;
  }

So if you know how to modify the last piece of code to change the holder in the struct, then that would be greatly appreciated

4

Sorry but I didn't understand very well your aim. Btw given your struct like this:

struct Lip {
    string name;
    uint256 id;
    uint256 dna;
    uint16 level;
    uint8 rarity;
    address payable holder;
  }

to update just one element, like the holder address you can do in this way:
Hp: lip is your object that need to be modified

lip.holder = 'insert here new address'

5

Hmmm

I don't quite follow what you mean... Could I try another?:

pragma solidity ^0.4.17;

contract Profile {
    struct User {
        uint256 fuel;
    }

    mapping(address => User) public users;
    string name;

    function createUser() public {
        users[msg.sender] = User({
            fuel: 5
        });
    }

    function getFuel() public view returns (uint256) {
        return users[msg.sender].fuel;
    }

    function setFuel(uint256 newFuel) public {
        users[msg.sender].fuel = newFuel;
    }
}

When I call(click) createUser, it updates fuel to have 5, how do I change the function setFuel to automatically add 10 to the current value, which is now 5?

6

Alright:

This code allows me to recharge the fuel level, and subtract 1 unit everytime the useFuel function i called:

Thank you for your help :slight_smile:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.2;

contract Profile {
    struct User {
        uint256 fuel;
    }

    mapping(address => User) public users;
    string name;

    function createUser() public {
        users[msg.sender] = User({
            fuel: 1
        });
    }

    function getFuel() public view returns (uint256) {
        return users[msg.sender].fuel;
    }

    function setFuel() public payable {
        uint256 newFuel = 5;
        users[msg.sender].fuel = newFuel;
    }

    function useFuel() public {
        uint256 newuseFuel = users[msg.sender].fuel;
        users[msg.sender].fuel = (newuseFuel - 1);
    }


}