ERC721ERC721 (대체 불가능 토큰 표준) abstract contract ERC721 { using Strings for uint256; string private _name; string private _symbol; mapping(uint256 tokenId => address) private _owners; constructor (string memory name_, string memory symbol_){ _name = name_; _symbol = symbol_; }} openzeppelin의 ERC721 분석https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC721/ERC721..
