此文档为个人整理学习使用,部分内容来源于网络,也期待能给你带来益处。
以太坊生态系统中的代币可以代表任何可以交易的东西:币(coin)、积分、黄金证券、欠条(IOU)等。
因为所有的代币都以标准化的方式实现一些基本的特性,这样意味着你自己创建的代币将于以太坊钱包、使用相同标准的任何其它客户端或者合约相兼容。
启动私链,在mist钱包中新建合约,把以下代码拷到合约窗口中,不同版本可能会有一些错误,自己简单改一下:
pragma solidity ^0.4.18;
contract MyToken {
/* Public variables of the token */
string public name;
string public symbol;
uint8 public decimals;
/* This creates an array with all balances */
mapping (address => uint256) public balanceOf;
/* This generates a public event on the blockchain that will notify clients */
event Transfer(address indexed from, address indexed to, uint256 value);
/* Initializes contract with initial supply tokens to the creator of the contract */
function MyToken(uint256 _supply, string _name, string _symbol, uint8 _decimals) public{
/* if supply not given then generate 1 million of the smallest unit of the token */
if (_supply == 0) _supply = 1000000;
/* Unless you add other functions these variables will never change */
balanceOf[msg.sender] = _supply;
name = _name;
symbol = _symbol;
/* If you want a divisible token then add the amount of decimals the base unit has */
decimals = _decimals;
}
/* Send coins */
function transfer(address _to, uint256 _value) private {
/* if the sender doenst have enough balance then stop */
if (balanceOf[msg.sender] < _value) return;
if (balanceOf[_to] + _value < balanceOf[_to]) return;
/* Add and subtract new balances */
balanceOf[msg.sender] -= _value;
balanceOf[_to] += _value;
/* Notifiy anyone listening that this transfer took place */
Transfer(msg.sender, _to, _value);
}
}
显示如下
在右边选择部署的合约为“MyToken”,右边更改系数定制自己的货币。
supply: 货币总量,name: 货币名字,symbol:货币符号,decimals:货币单位精确到小数点后几位。
如下图发行一个VIP标志,总数量为100个。
点击发布,输入密码确定等一会矿工确认后在“最新交易”中可以看到
点击“定制化合约”中刚创建的MyToken合约,选择右边的“复制地址”,这个地址在查看代币中要用到。
点击“定制化TOKEN”中的“查看代币”,粘贴地址到TOKEN地址,确定
这样就能看到刚创建的100个VIP标志的代币了!
点击左上角的“发送”,进入后选择刚才创建的帐号,因为现在只有这个帐号有代币,选择其它帐号看不到代币,只有ETHER,这个帐号下就有两种货币:ETHER和VF
例如我现在要给account2发送1个标志,把account2的地址“0x469f07278600b1cb031448fd25f187f24a89ecb6”粘贴到“发送至”输入框,数量为1,发送即可
不过我这私链上有问题,出现错误:
[2018-01-12T18:40:59.931] [ERROR] ipcProviderBackend - Send request failed { code: -32000,
message: 'gas required exceeds allowance or always failing transaction' }
其实mist钱包“定制化TOKEN”内就有两个链接说明如何创建代币的,如下:
https://ethereum.org/token#the-code
https://www.ethereum.org/token
那就找一个比较完整的代币代码直接粘贴过来吧
pragma solidity ^0.4.16;
interface tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) public; }
contract TokenERC20 {
// Public variables of the token
string public name;
string public symbol;
uint8 public decimals = 18;
// 18 decimals is the strongly suggested default, avoid changing it
uint256 public totalSupply;
// This creates an array with all balances
mapping (address => uint256) public balanceOf;
mapping (address => mapping (address => uint256)) public allowance;
// This generates a public event on the blockchain that will notify clients
event Transfer(address indexed from, address indexed to, uint256 value);
// This notifies clients about the amount burnt
event Burn(address indexed from, uint256 value);
/**
* Constrctor function
*
* Initializes contract with initial supply tokens to the creator of the contract
*/
function TokenERC20(
uint256 initialSupply,
string tokenName,
string tokenSymbol
) public {
totalSupply = initialSupply * 10 ** uint256(decimals); // Update total supply with the decimal amount
balanceOf[msg.sender] = totalSupply; // Give the creator all initial tokens
name = tokenName; // Set the name for display purposes
symbol = tokenSymbol; // Set the symbol for display purposes
}
/**
* Internal transfer, only can be called by this contract
*/
function _transfer(address _from, address _to, uint _value) internal {
// Prevent transfer to 0x0 address. Use burn() instead
require(_to != 0x0);
// Check if the sender has enough
require(balanceOf[_from] >= _value);
// Check for overflows
require(balanceOf[_to] + _value > balanceOf[_to]);
// Save this for an assertion in the future
uint previousBalances = balanceOf[_from] + balanceOf[_to];
// Subtract from the sender
balanceOf[_from] -= _value;
// Add the same to the recipient
balanceOf[_to] += _value;
Transfer(_from, _to, _value);
// Asserts are used to use static analysis to find bugs in your code. They should never fail
assert(balanceOf[_from] + balanceOf[_to] == previousBalances);
}
/**
* Transfer tokens
*
* Send `_value` tokens to `_to` from your account
*
* @param _to The address of the recipient
* @param _value the amount to send
*/
function transfer(address _to, uint256 _value) public {
_transfer(msg.sender, _to, _value);
}
/**
* Transfer tokens from other address
*
* Send `_value` tokens to `_to` on behalf of `_from`
*
* @param _from The address of the sender
* @param _to The address of the recipient
* @param _value the amount to send
*/
function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
require(_value <= allowance[_from][msg.sender]); // Check allowance
allowance[_from][msg.sender] -= _value;
_transfer(_from, _to, _value);
return true;
}
/**
* Set allowance for other address
*
* Allows `_spender` to spend no more than `_value` tokens on your behalf
*
* @param _spender The address authorized to spend
* @param _value the max amount they can spend
*/
function approve(address _spender, uint256 _value) public
returns (bool success) {
allowance[msg.sender][_spender] = _value;
return true;
}
/**
* Set allowance for other address and notify
*
* Allows `_spender` to spend no more than `_value` tokens on your behalf, and then ping the contract about it
*
* @param _spender The address authorized to spend
* @param _value the max amount they can spend
* @param _extraData some extra information to send to the approved contract
*/
function approveAndCall(address _spender, uint256 _value, bytes _extraData)
public
returns (bool success) {
tokenRecipient spender = tokenRecipient(_spender);
if (approve(_spender, _value)) {
spender.receiveApproval(msg.sender, _value, this, _extraData);
return true;
}
}
/**
* Destroy tokens
*
* Remove `_value` tokens from the system irreversibly
*
* @param _value the amount of money to burn
*/
function burn(uint256 _value) public returns (bool success) {
require(balanceOf[msg.sender] >= _value); // Check if the sender has enough
balanceOf[msg.sender] -= _value; // Subtract from the sender
totalSupply -= _value; // Updates totalSupply
Burn(msg.sender, _value);
return true;
}
/**
* Destroy tokens from other account
*
* 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 enough
require(_value <= allowance[_from][msg.sender]); // Check allowance
balanceOf[_from] -= _value; // Subtract from the targeted balance
allowance[_from][msg.sender] -= _value; // Subtract from the sender's allowance
totalSupply -= _value; // Update totalSupply
Burn(_from, _value);
return true;
}
}
这次把这个代币叫做和SuperVipFlag,如下
用这个代码都不用去“定制化TOKEN”的“查看代币”手动添加了,合约创建完就可以看到代币了,但是缺省是18位小数,实际这个标志是不可分割的。
而且这次发送SVF也不提示出错了,成功完成代币转移!
在用户钱包中也可以查看到代币的数量,不过这个mist版本显示有点问题,小数点为什么用“,”呢?!
https://www.ethereum.org/token
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