contract ERC20 {
//**********9个函数*******
//1.代币的名字
function name() constant public returns (string name);
//2.代币的简称，例如：HMB
function symbol() public constant returns (string symbol);
//3.代币的最小分割量 token使用的小数点后几位。比如如果设置为3，就是支持0.001表示
function decimals() public constant returns (uint8 decimals);
//4.token的总量
function totalSupply() public constant returns (uint totalSupply);
//5.余额 返回某个地址(账户)的账户余额
function balanceOf(address _owner) public constant returns (uint balance);
/*6.转账 交易代币 从消息发送者账户中往_to账户转数量为_value的token，
从代币合约的调用者地址上转移 _value的数量token到的地址 _to
【注意：并且必须触发Transfer事件】*/
function transfer(address _to, uint _value) public returns (bool success);
/*7.两个地址转账
从账户_from中往账户_to转数量为_value的token，与approve方法配合使用
从地址 _from发送数量为 _value的token到地址 _to
【注意：并且必须触发Transfer事件】
transferFrom方法用于允许合约代理某人转移token。条件是from账户必须经过了approve。*/
function transferFrom(address _from, address _to, uint _value) public returns (bool success);
//8.批准_spender能从合约调用账户中转出数量为_value的token
function approve(address _spender, uint _value) public returns (bool success);
//9.获取_spender可以从账户_owner中转出token的剩余数量
function allowance(address _owner, address _spender) public constant returns (uint remaining);
//**********2个事件*******
//1.发生转账时必须要触发的事件,transfer 和 transferFrom 成功执行时必须触发的事件
event Transfer(address indexed _from, address indexed _to, uint _value);
//2.当函数 approve(address _spender, uint256 _value)成功执行时必须触发的事件
event Approval(address indexed _owner, address indexed _spender, uint _value);
//10.存储(映射)对账号的控制:mapping(owner => mapping(spender => amount)) allowed
第一个address表示token拥有者
第二个address表示授权的spender，即spender代理消费owner的token
第三个amout表示代理的数量
这是一个map的嵌套使用
// 此合约实现不记得是哪看到后复制保存的......和官网案例类似pragma solidity ^0.4.25;interface tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) public; }contract TokenERC20 {string public name; // ERC20标准string public symbol; // ERC20标准uint8 public decimals = 2; // ERC20标准，decimals 可以有的小数点个数，最小的代币单位。18 是建议的默认值uint256 public totalSupply; // ERC20标准 总供应量// 用mapping保存每个地址对应的余额 ERC20标准mapping (address => uint256) public balanceOf;// 存储对账号的控制 ERC20标准mapping (address => mapping (address => uint256)) public allowance;// 事件，用来通知客户端交易发生 ERC20标准event Transfer(address indexed from, address indexed to, uint256 value);// 事件，用来通知客户端代币被消费 ERC20标准event Burn(address indexed from, uint256 value);/*** 初始化构造*/function TokenERC20(uint256 initialSupply, string tokenName, string tokenSymbol) public {totalSupply = initialSupply * 10 ** uint256(decimals); // 供应的份额，份额跟最小的代币单位有关，份额 = 币数 * 10 ** decimals。balanceOf[msg.sender] = totalSupply;// 创建者拥有所有的代币name = tokenName;// 代币名称symbol = tokenSymbol; // 代币符号}/*** 代币交易转移的内部实现*/function _transfer(address _from, address _to, uint _value) internal {// 确保目标地址不为0x0，因为0x0地址代表销毁require(_to != 0x0);// 检查发送者余额require(balanceOf[_from] >= _value);// 确保转移为正数个require(balanceOf[_to] + _value > balanceOf[_to]);// 以下用来检查交易，uint previousBalances = balanceOf[_from] + balanceOf[_to];// Subtract from the senderbalanceOf[_from] -= _value;// Add the same to the recipientbalanceOf[_to] += _value;Transfer(_from, _to, _value);// 用assert来检查代码逻辑。assert(balanceOf[_from] + balanceOf[_to] == previousBalances);}/*** 代币交易转移* 从自己（创建交易者）账号发送`_value`个代币到 `_to`账号* ERC20标准* @param _to 接收者地址* @param _value 转移数额*/function transfer(address _to, uint256 _value) public {_transfer(msg.sender, _to, _value);}/*** 账号之间代币交易转移* ERC20标准* @param _from 发送者地址* @param _to 接收者地址* @param _value 转移数额*/function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {require(_value <= allowance[_from][msg.sender]);// Check allowanceallowance[_from][msg.sender] -= _value;_transfer(_from, _to, _value);return true;}/*** 设置某个地址（合约）可以创建交易者名义花费的代币数。** 允许发送者`_spender` 花费不多于 `_value` 个代币* ERC20标准* @param _spender The address authorized to spend* @param _value the max amount they can spend*/function approve(address _spender, uint256 _value) publicreturns (bool success) {allowance[msg.sender][_spender] = _value;return true;}/*** 设置允许一个地址（合约）以我（创建交易者）的名义可最多花费的代币数。*-非ERC20标准* @param _spender 被授权的地址（合约）* @param _value 最大可花费代币数* @param _extraData 发送给合约的附加数据*/function approveAndCall(address _spender, uint256 _value, bytes _extraData)publicreturns (bool success) {tokenRecipient spender = tokenRecipient(_spender);if (approve(_spender, _value)) {// 通知合约spender.receiveApproval(msg.sender, _value, this, _extraData);return true;}}/*** 销毁我（创建交易者）账户中指定个代币*-非ERC20标准*/function burn(uint256 _value) public returns (bool success) {require(balanceOf[msg.sender] >= _value); // Check if the sender has enoughbalanceOf[msg.sender] -= _value; // Subtract from the sendertotalSupply -= _value; // Updates totalSupplyBurn(msg.sender, _value);return true;}/*** 销毁用户账户中指定个代币*-非ERC20标准* Remove `_value` tokens from the system irreversibly on behalf of `_from`.** @param _from the address of the sender* @param _value the amount of money to burn*/function burnFrom(address _from, uint256 _value) public returns (bool success) {require(balanceOf[_from] >= _value);// Check if the targeted balance is enoughrequire(_value <= allowance[_from][msg.sender]); // Check allowancebalanceOf[_from] -= _value;// Subtract from the targeted balanceallowance[_from][msg.sender] -= _value; // Subtract from the sender's allowancetotalSupply -= _value;// Update totalSupplyBurn(_from, _value);return true;}}
