如何防止用户将他们从我的平台上获得的NFTs销售到像openSea这样的外部市场

Question

我正在构建我的平台，用户将做几个任务来赚取NFT作为回报，我不希望他们在任何外部市场上出售这些NFT。是否有一种方法可以限制我的NFT仅限于我的生态系统？如果有人有任何建议，请告诉我！

Answer 1

我看到3种可能的选择，取决于哪些最适合当前和未来的用例用于您的合同：

合同XXX是ERC721，拥有{}

1-您可以重写_safeTransferFrom函数，以包含暂停所有传输的选项(如果暂停= true，则禁用所有传输，包括销售)：

bool public transfersPaused = false;

function safeTransferFrom(address from, address to, uint256 tokenId) public virtual override {
        require(transfersPaused = false), "transfers paused")
        safeTransferFrom(from, to, tokenId, "");
    }

function setTransfersPaused(bool _setPause) public onlyOwner {
        transfersPaused = _setPause;
    }

2-你也可以黑名单/阻止特定的合同地址(市场=经营者)从启动转移(如果你确定了他们的地址)。

bool public transfersPaused = false;
address[] public blockedOperators;

function blockOperators(address[] calldata _blockList) public onlyOwner {
    delete blockedOperators;
    blockedOperators = _blockList;
}

function isBlocked(address _contract) public view returns (bool) {
    for (uint i = 0; i < blockedOperators.length; i++) {
        if (blockedOperators[i] == _contract) {
        return true;
        }
    }
    return false;
}

function setTransfersPaused(bool _setPause) public onlyOwner {
    transfersPaused = _setPause;
}

function safeTransferFrom(address from, address to, uint256 tokenId) public virtual override {
    require(transfersPaused = false, "transfers paused");
    if (isBlocked(msg.sender) == true) {
        revert("no transfer allowed");
    }
    safeTransferFrom(from, to, tokenId, "");
}

3-与_safeTransferFrom函数类似，您也可以对_setApprovalForAll函数进行操作。它限制了对代表用户管理令牌所需的操作员批准的访问(这基本上阻碍了大多数市场交换令牌的能力)。

bool public approvalsPaused = false;
mapping(address => mapping(address => bool)) private _operatorApprovals;

function _setApprovalForAll(address owner, address operator, bool approved) internal virtual override {
    require(owner != operator, "ERC721: approve to caller");
    require(approvalsPaused = false, "Approvals paused");
            if (isBlocked(msg.sender) == true) {
        revert("no transfer allowed");
    }
    _operatorApprovals[owner][operator] = approved;
    emit ApprovalForAll(owner, operator, approved);
}

请注意，任何已授予的审批(先前的限制)都不能用此代码撤销。您还需要将blockOperators和isBlocked函数包含到合同中(参见2)

Answer 2

是啊，只要关掉传输功能就行了。如果您正在使用openzeppelin，那么您可以这样做，只需添加此代码，传输函数将始终恢复。即使您没有使用openzeppelin，这也会起作用，您只需要移除重载关键字，因为这里不需要它。

function _safeBatchTransferFrom(
        address from,
        address to,
        uint256[] memory ids,
        uint256[] memory amounts,
        bytes memory data
    ) internal pure override {
        revert("No batch transfer allowed");
    }

      function _safeTransferFrom(
        address from,
        address to,
        uint256 id,
        uint256 amount,
        bytes memory data
    ) internal pure override {
        revert("no transfer allowed");