interface ERC721 {

    event Transfer(address indexed _from, address indexed _to, uint256 indexed _tokenId);
    event Approval(address indexed _owner, address indexed _approved, uint256 indexed _tokenId);
    event ApprovalForAll(address indexed _owner, address indexed _operator, bool _approved);
    function balanceOf(address _owner) external view returns (uint256);
    function ownerOf(uint256 _tokenId) external view returns (address);
    function safeTransferFrom(address _from, address _to, uint256 _tokenId, bytes data) external payable;
    function safeTransferFrom(address _from, address _to, uint256 _tokenId) external payable;
    function transferFrom(address _from, address _to, uint256 _tokenId) external payable;
    function approve(address _approved, uint256 _tokenId) external payable;
    function setApprovalForAll(address _operator, bool _approved) external;
    function getApproved(uint256 _tokenId) external view returns (address);
    function isApprovedForAll(address _owner, address _operator) external view returns (bool);
}

interface ERC165 {
    function supportsInterface(bytes4 interfaceID) external view returns (bool);
}

interface ERC721TokenReceiver {
    function onERC721Received(address _operator, address _from, uint256 _tokenId, bytes _data) external returns(bytes4);
}			
			
			

可选实现接口，ERC721Metadata 接口用于提供合约的元数据：name , symbol 及 URI（NFT所对应的资源）。

			
其接口定义如下：

interface ERC721Metadata /* is ERC721 */ {
    function name() external pure returns (string _name);
    function symbol() external pure returns (string _symbol);
    function tokenURI(uint256 _tokenId) external view returns (string);
}

接口说明：
name(): 返回合约名字，尽管是可选，但强烈建议实现，即便是返回空字符串。
symbol(): 返回合约代币符号，尽管是可选，但强烈建议实现，即便是返回空字符串。
tokenURI(): 返回_tokenId所对应的外部资源文件的URI（通常是IPFS或HTTP(S)路径）。外部资源文件需要包含名字、描述、图片，其格式的要求如下：			
			
			

可选实现接口，ERC721Enumerable的主要目的是提高合约中NTF的可访问性，其接口定义如下：

			
interface ERC721Enumerable /* is ERC721 */ {
    function totalSupply() external view returns (uint256);
    function tokenByIndex(uint256 _index) external view returns (uint256);
    function tokenOfOwnerByIndex(address _owner, uint256 _index) external view returns (uint256);
}
接口说明：

totalSupply(): 返回NFT总量
tokenByIndex(): 通过索引返回对应的tokenId。
tokenOfOwnerByIndex(): 所有者可以一次拥有多个的NFT, 此函数返回_owner拥有的NFT列表中对应索引的tokenId。