ERC20与ERC721标准及案例
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ERC-20
ERC-20简介
数字加密货币可以分为原生币和代币(token)。ERC(Etherum Request for Comments)是以太坊开发者针对代币提交的协议提案,而20表示的是协议的编号。所有符合ERC-20标准的代币都能立即兼容以太坊钱包,并且降低了token的开发门槛,只要实现ERC-20协议就可以快速开发出一种新的token。除此之外,通过实现ERC标准还增加了合约之间的互操作性、token的安全性。但是ERC-20也有着一些缺陷,比如:发布后不能修改合约、如果向合约中发送的不是ETH,而是其他token,那么智能合约将不能退还你发送的token。
这个网站列举了所有的ERC协议,可以进行参考:https://eips.ethereum.org/erc
ERC-20代币标准
- 最小单元:6个函数,2个事件
- totalSupply:获取token的总发行量
function totalSupply() public view returns (uint256)
- balanceOf:获取_owner代币token
function balanceOf(address _owner) public view returns (uint256 balance)
- transfer:向_to转入_value的token
function transfer(address _to, uint256 _value) public returns (bool success)
- transferFrom:从_from向_to转入_value的token
function transferFrom(address _from, address _to, uint256 _value) public returns (bool success)
- approve:授权token
function approve(address _spender, uint256 _value) public returns (bool success)
- allowance:返回剩余token使用的数量
function allowance(address _owner, address _spender) public view returns (uint256 remaining)
- Transfer:转账事件
event Transfer(address indexed _from, address indexed _to, uint256 _value)
- Approval:授权提款事件
event Approval(address indexed _owner, address indexed _spender, uint256 _value)
- totalSupply:获取token的总发行量
- 可选单元:3个函数
- Name:token的名称
function name() public view returns (string)
- Symbol:token的logo标识
function symbol() public view returns (string)
- Decimals:按小数返回,例如输入360000000转化为3.6
function decimals() public view returns (uint8)
- Name:token的名称
ERC-20案例
//------ERC20.sol
pragma solidity 0.6.0;
abstract contract ERC20
function totalSupply() virtual public view returns (uint256);
function balanceOf(address _owner) virtual public view returns (uint256 balance);
function transfer(address _to, uint256 _value) virtual public returns (bool success);
function transferFrom(address _from, address _to, uint256 _value) virtual public returns (bool success);
function approve(address _spender, uint256 _value) virtual public returns (bool success);
function allowance(address _owner, address _spender) virtual public view returns (uint256 remaining);
event Transfer(address indexed _from, address indexed _to, uint256 _value);
event Approval(address indexed _owner, address indexed _spender, uint256 _value);
//-------myERC20.sol
pragma solidity ^0.6.0;
import "./ERC20.sol";
// 实现安全运算
contract SafeMath
function safeMul(uint256 a, uint256 b) internal returns (uint256)
uint256 c = a * b;
assert(a == 0 || c / a == b);
return c;
function safeDiv(uint256 a, uint256 b) internal returns (uint256)
assert(b > 0);
uint256 c = a / b;
assert(a == b * c + a % b);
return c;
function safeSub(uint256 a, uint256 b) internal returns (uint256)
assert(b <= a);
return a - b;
function safeAdd(uint256 a, uint256 b) internal returns (uint256)
uint256 c = a + b;
assert(c>=a && c>=b);
return c;
function assert(bool assertion) internal
if (!assertion)
revert();
contract SafeMath
function safeMul(uint256 a, uint256 b) internal returns (uint256)
uint256 c = a * b;
assert(a == 0 || c / a == b);
return c;
function safeDiv(uint256 a, uint256 b) internal returns (uint256)
assert(b > 0);
uint256 c = a / b;
assert(a == b * c + a % b);
return c;
function safeSub(uint256 a, uint256 b) internal returns (uint256)
assert(b <= a);
return a - b;
function safeAdd(uint256 a, uint256 b) internal returns (uint256)
uint256 c = a + b;
assert(c>=a && c>=b);
return c;
function assert(bool assertion) internal
if (!assertion)
revert();
contract myERC20 is ERC20, SafeMath
address public payable owner; // 定义合约拥有者
uint256 _totalSupply; // token发行总量
mapping(address => uint256) _balance; // 地址拥有的token
mapping(address => mapping(address => uint256)) approve; // 地址授权给另一个地址token
event Transfer(address indexed _from, address indexed _to, uint256 _value);
event Approval(address indexed _owner, address indexed _spender, uint256 _value);
// 构造函数,初始化token总量、合约拥有者。
constructor(uint256 totalSupply) public
_totalSupply = totalSupply;
_owner = msg.sender;
modifier onlyOwner()
require(msg.sender == _owner);
_;
// 向_to中空投_value的token
function airDrop (address _to, uint256 _value) onlyOwer public
require(_to != address(0));
_balance[_to] = SafeMath.safeAdd(_balance[_to], _value);
_totalSupply = SafeMath.safeAdd(_totalSupply, _value);
// 返回token总量
function totalSupply() override public view returns (uint256)
return _totalSupply;
// 返回_owner拥有token的数量
function balanceOf(address _owner) override public view returns (uint256 balance)
require(owner != address(0));
return _balance[_owner];
// 向_to中转入_value的token
function transfer(address _to, uint256 _value) override public returns (bool success)
require(_to != address(0));
require(_value > 0);
require(_balance[msg.sender] >= _value);
_balance[msg.sender] = SafeMath.safeSub(_balance[msg.sender], _value);
_balance[_to] = SafeMath.safeAdd(_balance[_to], _value);
emit Transfer( msg.sender, _to, _value);
return true;
// 从_from向_to转入_value的token
function transferFrom(address _from, address _to, uint256 _value) override public returns (bool success)
require(_from != address(0));
require(_to != address(0));
require(_approve[_from][msg.sender] >= _value);
_approve[_from][msg.sender] = SafeMath.safeSub(_approve[_from][msg.sender], _value);
_balance[_to] = SafeMath.safeAdd(_balance[_to], _value);
emit Transfer(_from, _to, _value);
return true;
// 授权给_spender _value数量的token
function approve(address _spender, uint256 _value) override public returns (bool success)
require(_spender != address(0));
require(_balance[msg.sender] >= _value);
_approve[msg.sender][_spender] = SafeMath.safeAdd(_approve[msg.sender][_spender], _value);
_balance[msg.sender] = SafeMath.safeSub(_balance[msg.sender], _value);
emit Approval(msg.sender, _spender, _value);
return true;
// 查询_owner向_spender授权了多少token
function allowance(address _owner, address _spender) override public view returns (uint256 remaining)
require(_owner != address(0));
require(_spender != address(0));
return _approve[_owner][_spender];
// 提取token
function withdrawEther(uint256 _value) public
require(msg.sender == owner);
owner.transfer(_value);
ERC-721
ERC-721简介
ERC-721官方的解释是:Non-Fungible Tokens(非同质化代币),简写为NFT。实现了ERC-72协议的token,每个都有自己的唯一性和独特价值,并且不可分割。目前主要适用于收藏品、游戏等需要确定唯一性资产的场景。
ERC-721代币标准
- 最小单元:9个函数,3个事件
- 获取分配给owner的所以NFT数量
function balanceOf(address _owner) external view returns (uint256);
- 查询拥有token ID号为tokenid的NFT的所属者owner地址
function ownerOf(uint256 _tokenId) external view returns (address);
- 将token ID号为tokenId的NFT的NFT从_from地址的用户转移到_to地址的用户
function transferFrom(address _from, address _to, uint256 _tokenId) external payable;
- 将token ID号为_tokenId的NFT从_from地址的用户转移到_to地址的用户,并携带data数据
function safeTransferFrom(address _from, address _to, uint256 _tokenId, bytes data) external payable;
- 将token ID号为_tokenId的NFT从_from地址的用户转移到_to地址的用户
function safeTransferFrom(address _from, address _to, uint256 _tokenId) external payable;
- 向_approved进行授权
function approve(address _approved, uint256 _tokenId) external payable;
- 获取_tokenId代币对应的拥有者地址address
function getApproved(uint256 _tokenId) external view returns (address);
- 授权给第三方_operate进行管理个人的ERC721代币token资产
function setApprovalForAll(address _operator, bool _approved) external;
- 查看_owner是否授权_operate管理所有的ERC721代币token资产
function isApprovedForAll(address _owner, address _operator) external view returns (bool);
- NFT资产转移事件
event Transfer(address indexed _from, address indexed _to, uint256 indexed _tokenId);
- NFT资产授权地址发生变更事件
event Approval(address indexed _owner, address indexed _approved, uint256 indexed _tokenId);
- 所有NFT资产被授权事件
event ApprovalForAll(address indexed _owner, address indexed _operator, bool _approved);
- 获取分配给owner的所以NFT数量
- 可选单元
- 描述NFT收藏品的名称
function name() external view returns (string _name);
- 合约中NTF名称的缩写
function symbol() external view returns (string _symbol);
- 给定资产唯一资源标识符(URI)对应的详细信息
function tokenURI(uint256 _tokenId) external view returns (string);
- 追踪计数合约中的NFT数量
function totalSupply() external view returns (uint256);
- 枚举有效的NFT
function tokenByIndex(uint256 _index) external view returns (uint256);
- 枚举分配给拥有者的NFT
function tokenOfOwnerByIndex(address _owner, uint256 _index) external view returns (uint256);
- 描述NFT收藏品的名称
ERC-721案例
//---ERC721.sol
pragma solidity ^0.6.0;
abstract contract ERC721
function balanceOf(address _owner) virtual external view returns (uint256);
function ownerOf(uint256 _tokenId) virtual external view returns (address);
function transferFrom(address _from, address _to, uint256 _tokenId) virtual external payable;
function safeTransferFrom(address _from, address _to, uint256 _tokenId) virtual external payable;
function safeTransferFrom(address _from, address _to, uint256 _tokenId, byte data) virtual external payable;
function approve(address _approved, uint256 _tokenId) virtual external payable;
function setApprovalForAll(address _operator, bool _approved) virtual external;
function getApproved(uint256 _tokenId) virtual external view returns (address);
function isApprovedForAll(address _owner, address _operator) virtual external view returns (bool);
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);
//-----myArt.sol
pragma solidity ^0.6.0;
import "./ERC721.sol";
contract pcArtCoin is ERC721
// 合约拥有者
address public fundation;
// 资产结构体
struct asset
uint256 _tokenId; // token ID
address owner; // token 拥有者地址
address approver; // token 被授权的地址
uint256 timestamp; // 时间戳
byte data; // token 中包含的数据
// 地址拥有的NFT数量
mapping(address => uint256) balances;
// NFT编号对应的资产
mapping(uint256 => asset) tokens;
// 授权
mapping(address => mapping(address => bool)) isAllProved;
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);
// 设置资产
function setAssert(uint256 number, address owner, byte data) onlyFundation public
require(owner != address(0));
// 生产随机的token ID
uint256 tokenId = uint256(keccak256(abi.encodePacked(number, msg.sender, now, owner, data)));
// 保证token ID不同
require(tokens[tokenId]._tokenId != tokenId);
// 设置资产
asset memory Asset = asset(tokenId, owner, address(0), now, data);
tokens[tokenId] = Asset;
modifier onlyFundation()
require(msg.sender == fundation);
_;
// 返回_owner拥有NFT的数量
function balanceOf(address _owner) override external view returns (uint256)
require(_owner != address(0));
return balances[_owner];
// 返回_tokenId的拥有者
function ownerOf(uint256 _tokenId) override external view returns (address)
require(_tokenId != 0);
return tokens[_tokenId].owner;
// 从_from转到_to, NFT编号为_tokenId
function transferFrom(address _from, address _to, uint256 _tokenId) override external payable
// 安全检查
require(tokens[_tokenId].owner == _from);
require(_from != address(0) && _to != address(0) && _tokenId != 0);
require(msg.sender == _from || tokens[_tokenId].approver == msg.sender);
tokens[_tokenId].owner = _to;
tokens[_tokenId].approver = address(0);
tokens[_tokenId].timestamp = now;
tokens[_tokenId].data = byte("");
balances[_from] -= 1;
balances[_to] += 1;
emit Transfer(_from, _to, _tokenId);
function safeTransferFrom(address _from, address _to, uint256 _tokenId) override external payable
require(tokens[_tokenId].approver == _from);
// 判断_to不为合约地址
require(addrCheck(_to));
require(_from != address(0) && _to != address(0) && _tokenId != 0);
require(msg.sender == _from || tokens[_tokenId].approver == msg.sender);
tokens[_tokenId].owner = _from;
tokens[_tokenId].approver = address(0);
tokens[_tokenId].timestamp = now;
tokens[_tokenId].data = byte("");
balances[_from] -= 1;
balances[_to] += 1;
emit Transfer(_from, _to, _tokenId);
function safeTransferFrom(address _from, address _to, uint256 _tokenId, byte data) override external payable
require(tokens[_tokenId].owner == _from);
require(addrCheck(_to));
require(_from != address(0) && _to != address(0) && _tokenId != 0);
require(msg.sender == _from || tokens[_tokenId].approver == msg.sender);
tokens[_tokenId].owner = _to;
tokens[_tokenId].approver = address(0);
tokens[_tokenId].timestamp = now;
tokens[_tokenId].data = data;
balances[_from] -= 1;
balances[_to] += 1;
emit Transfer(_from, _to, _tokenId);
function approve(address _approved, uint256 _tokenId) override external payable
require(tokens[_tokenId].owner == msg.sender);
require(_tokenId != 0);
tokens[_tokenId].approver = _approved;
emit Approval(msg.sender, _approved, _tokenId);
// 向_operator 授权操作
function setApprovalForAll(address _operator, bool _approved) override external
require(_operator != address(0));
require(isAllProved[msg.sender][_operator] != _approved);
isAllProved[msg.sender][_operator] = _approved;
emit ApprovalForAll(msg.sender, _operator, _approved);
// 获取 _tokenId token的被授权人
function getApproved(uint256 _tokenId) override external view returns (address)
require(_tokenId != 0);
return tokens[_tokenId].approver;
function isApprovedForAll(address _owner, address _operator) override external view returns (bool)
require(_owner != address(0) || _operator != address(0));
return isAllProved[_owner][_operator];
// 判断是否为合约地址,是返回false,不是返回true
function addrCheck(address _addr) private view returns (bool)
uint256 size;
assembly
size := extcodesize(_addr)
require(size == 0);
return true;
最后
如果代码有不足之处,欢迎评论区指出。另外推荐一个github地址,上面有许多区块链学习资源及技术文章,同样欢迎参观,一起学习进步:https://github.com/mindcarver。
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