... virtual {
_transfer(from, to, tokenId);
require(_checkOnERC721Received(from, to, tokenId, _data), "ERC721: transfer to non ERC721Receiver implementer");
}
````
先执行了_transfer函数后执行_checkOnERC721Received函数,而后者是为了检测to这个参数是否...
ERC721的Token不能在一个合约方法中授权并转移吗?
```
IERC721(tokenadr).approve(address(this), _nftid);
IERC721(tokenadr).safeTransferFrom(msg.sender, address(this), _nftid);
```
上面这个方法会报错:ERC721: approve caller is not owner nor approved for all