一、Token 合约代码示例
Token 合约代码示例如下，实现功能 ERC20。
/*SPDX-License-Identifier: Apache-2.0*/pragma solidity >0.5.11;contract Token { string public name = "token"; // token name string public symbol = "TK"; // token symbol uint256 public decimals = 6; // token digit mapping (address => uint256) public balanceOf; mapping (address => mapping (address => uint256)) public allowance; uint256 public totalSupply = 0; bool public stopped = false; uint256 constant valueFounder = 100000000000000000; address owner = address (0x0); modifier isOwner { assert (owner == msg.sender); _; } modifier isRunning { assert (!stopped); _; } modifier validAddress { assert (address (0x0) != msg.sender); _; } constructor (address _addressFounder) { owner = msg.sender; totalSupply = valueFounder; balanceOf [_addressFounder] = valueFounder; emit Transfer (address (0x0), _addressFounder, valueFounder); } function transfer (address _to, uint256 _value) public isRunning validAddress returns (bool success) { require (balanceOf [msg.sender] >= _value); require (balanceOf [_to] + _value >= balanceOf [_to]); balanceOf [msg.sender] -= _value; balanceOf [_to] += _value; emit Transfer (msg.sender, _to, _value); return true; } function transferFrom (address _from, address _to, uint256 _value) public isRunning validAddress returns (bool success) { require (balanceOf [_from] >= _value); require (balanceOf [_to] + _value >= balanceOf [_to]); require (allowance [_from][msg.sender] >= _value); balanceOf [_to] += _value; balanceOf [_from] -= _value; allowance [_from][msg.sender] -= _value; emit Transfer (_from, _to, _value); return true; } function approve (address _spender, uint256 _value) public isRunning validAddress returns (bool success) { require (_value == 0 || allowance [msg.sender][_spender] == 0); allowance [msg.sender][_spender] = _value; emit Approval (msg.sender, _spender, _value); return true; } function stop () public isOwner { stopped = true; } function start () public isOwner { stopped = false; } function setName (string memory _name) public isOwner { name = _name; } function burn (uint256 _value) public { require (balanceOf [msg.sender] >= _value); balanceOf [msg.sender] -= _value; balanceOf [address (0x0)] += _value; emit Transfer (msg.sender, address (0x0), _value); } event Transfer (address indexed _from, address indexed _to, uint256 _value); event Approval (address indexed _owner, address indexed _spender, uint256 _value);}
二、Token 合约代码说明
| 参数名称 | 描述 |
| constructor | 合约构造函数，在合约部署时被调用，将 _addressFounder 的余额设置为 valueFounder。 |
| transfer | 转账函数，该函数具有两个入参，接收者地址 _to 和转账金额 _value，该函数将调用者 msg.sender 的余额减去 _value，将接收者的余额加上 _value。 |
| transferFrom | 转账函数，该函数具有三个入参，转账者地址 _from，接收者地址 _to 和转账金额 _value，该函数将转账者 _from 的余额减去 _value，将接收者的余额加上 _value。 |
| approve | 批准函数，该函数具有两个入参，接收者地址 _spender 和 token 数量 _value，该函数将接收者 _spender 可以从调用者 msg.sender 处转出的 token 数量设置为 _value。 |
| stop | 停止函数，该函数执行后，transfer，transferFrom 和 approve 函数将不能再被执行。 |
| start | 启动函数，该函数执行后，transfer，transferFrom 和 approve 函数将可以再被执行。 |
| setName | 设置 token 名字函数，该函数具有一个入参 _name，将 token 的名字设置为 _name。 |
| burn | 销毁函数，该函数具有一个入参 _value，将调用者 msg.sender 的余额减去 _value。 |