solidity ethereum blockchain

Ethereum智能合約 101

Posted by Benjamin Lu on 2017-08-23

Ethereum智能合約 101

安裝go-ethereum

Mac

Windows或其他版本

開啟一個私有鏈開發節點

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geth --dev
WARN [07-03|13:08:30] No etherbase set and no accounts found as default
INFO [07-03|13:08:30] Starting peer-to-peer node               instance=Geth/v1.6.5-stable-cf87713d/darwin-amd64/go1.8.3
INFO [07-03|13:08:30] Allocated cache and file handles         database=/var/folders/hs/tgqs62993t9gkrkr86d7z2hc0000gn/T/ethereum_dev_mode/geth/chaindata cache=128 handles=1024
INFO [07-03|13:08:30] Initialised chain configuration          config="{ChainID: 1337 Homestead: 0 DAO: <nil> DAOSupport: false EIP150: 0 EIP155: 0 EIP158: 0 Metropolis: 0 Engine: ethash}"
WARN [07-03|13:08:30] Ethash used in test mode
INFO [07-03|13:08:30] Initialising Ethereum protocol           versions="[63 62]" network=1
INFO [07-03|13:08:30] Loaded most recent local header          number=0 hash=e5be92…38f3bc td=131072
INFO [07-03|13:08:30] Loaded most recent local full block      number=0 hash=e5be92…38f3bc td=131072
INFO [07-03|13:08:30] Loaded most recent local fast block      number=0 hash=e5be92…38f3bc td=131072
INFO [07-03|13:08:30] Starting P2P networking
INFO [07-03|13:08:30] started whisper v.5.0
INFO [07-03|13:08:30] RLPx listener up                         self="enode://f7a7c9f414faa49e0e6bb72c1bddead9c6f8074e48323d444c23cafffb3583b42ab0dd496053f81f76004a4931228cce5989a3227130be42c7dd81e3332d4831@[::]:65282?discport=0"
INFO [07-03|13:08:30] IPC endpoint opened: /var/folders/hs/tgqs62993t9gkrkr86d7z2hc0000gn/T/ethereum_dev_mode/geth.ipc

上方會顯示測試鏈放置資料的路徑.../chaindata資料夾底下
network=1表示要跟此節點互相同步區塊要設定的subnet id
同時創世區塊要相同，且透過admin.addPeer()指令進行p2p網路的溝通
之後透過指定的ipc可以跟這個節點溝通，此案例是/var/folders/hs/tgqs62993t9gkrkr86d7z2hc0000gn/T/ethereum_dev_mode/geth.ipc

透過Geth JavaScript console 連接節點

此例IPC是/var/folders/hs/tgqs62993t9gkrkr86d7z2hc0000gn/T/ethereum_dev_mode/geth.ipc

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geth attach <IPC path>

操作節點指令

官方文件

Account

Account列表

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eth.accounts

創一個新帳號

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personal.newAccount("your password")
"0x4560eb5a01478cbfa1390a4134cd752d99746266"

解鎖帳號才能做交易

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personal.unlockAccount("0x4560eb5a01478cbfa1390a4134cd752d99746266", "your password")
true

以後開啟節點直接解鎖

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geth --dev --unlock 0x4560eb5a01478cbfa1390a4134cd752d99746266
...
Passphrase: <your password>

控制Miner

預設用第一個account的地址作為coinbase地址
所以開始挖礦以後，coinbase地址就會有錢

用PoA還是PoW的設定可以看meetup的文章

公網在PoS上線前，還是用PoW算sha3()
PoA 不用挖礦，只需要指定節點做Authority

Parity 1.5版 (Rust語言撰寫)以後支援建立Proof of Authority Chains
geth 1.6 (Go語言撰寫)之後支援PoA
但兩者的PoA根據不同的EIP來實作

geth實作的PoA為EIPs 225
稱Clique PoA protocol

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miner.start() // 開始挖礦 coinbase地址會有ETH讓你做交易或轉帳
miner.start(3) // 同時3條thread在挖礦
miner.stop() // 結束挖礦
eth.mining // 看是不是在挖礦
eth.coinbase // 礦工會得到虛擬貨幣獎勵的地址
miner.setEtherbase(eth.accounts[2]) // 換礦工地址

交易相關指令

你有多少錢

Ether unit單位表

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eth.getBalance("0x4560eb5a01478cbfa1390a4134cd752d99746266")
120000000000000000000 // 單位是wei, 1 ether = 10的負18次方個wei
web3.fromWei(eth.getBalance(eth.accounts[0])) // 第0個地址有多少ETH
web3.toWei(120) // 120個ether是多少個wei
"120000000000000000000"

做一個轉帳交易

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> eth.accounts
["0x4560eb5a01478cbfa1390a4134cd752d99746266", "0xcd9f3bf82cce5a654a6e7f729200f86dc9cc96c7"]

從0x4560eb5a01478cbfa1390a4134cd752d99746266轉帳1個ETH到0xcd9f3bf82cce5a654a6e7f729200f86dc9cc96c7

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eth.sendTransaction({
    from: "0x4560eb5a01478cbfa1390a4134cd752d99746266", 
    to: "0xcd9f3bf82cce5a654a6e7f729200f86dc9cc96c7" 
    value: web3.toWei(1)
})
"0x4aa3627a3cc245542cf57c51036689216371bfb373744186f229207fb63cbdf7"
eth.getTransaction("0x4aa3627a3cc245542cf57c51036689216371bfb373744186f229207fb63cbdf7")
{
  blockHash: "0xd14ff6de146210fc3b27e9771faa932de12a9abf721b12aaef88088d8d1395ae",
  blockNumber: 136,
  from: "0x4560eb5a01478cbfa1390a4134cd752d99746266",
  gas: 90000, // 花掉的gas
  gasPrice: 0, // 私有鏈沒有gasPrice的問題
  hash: "0x4aa3627a3cc245542cf57c51036689216371bfb373744186f229207fb63cbdf7",
  input: "0x",
  nonce: 0, // 用這個值在處理double spending
  r: "0xebd558f63d574a0002ba3be4b495c058ab6ad6d1803d1eb1bc10fa01e9be32e7",
  s: "0x81d5efa2f81a7e11e639ff9a64aa9554f8bab9fe0bf43995ae3b63d4eb4fa1e",
  to: "0xcd9f3bf82cce5a654a6e7f729200f86dc9cc96c7",
  transactionIndex: 0,
  v: "0xa95",
  value: 1000000000000000000
}
web3.fromWei(eth.getBalance("0xcd9f3bf82cce5a654a6e7f729200f86dc9cc96c7")) // 的確收到1ETH

智能合約 101 - Solidity為例

Ethereum的EVM上智能合約語言有以下幾種:

  1. Solidity (Javascript-like)
  2. Viper (Python-like)
  3. Serpent (Python-like)
  4. LLL (Lisp-like)
  5. Mutan (Golang-like)

這邊用Solidity當作寫合約的語言

智能合約IDE

Remix 線上IDE

常用關鍵字

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// 部署合約或呼叫合約的人
msg.sender
// 部署或呼叫合約的人付的錢
msg.value
// 合約的餘額
this.balance
// 由合約的錢轉帳this.balance數量的虛擬貨幣給address，會在鏈上形成交易
address.transfer(this.balance);
// 合約方法會需要收ether需要加關鍵字payable
// 沒有加的話呼叫該函式順便帶ether的話就會造成error
function pledge(bytes32 _message) payable {
    if (msg.value == 0 || complete || refunded) revert(); // 權限管控 不合格 停止執行 回復合約狀態
    pledges[numPledges] = Pledge(msg.value, msg.sender, _message);
    numPledges++;
}
// 使用其他合約物件，要寫路徑和副檔名
import "Another.sol"
// 毀滅合約，將合約餘額轉給某個地址
// 當合約被銷毀, 如果有人再寄錢 (Ethers) 到該合約地址, 是不會被退回的, 它也就此消失
suicide(address)
// 0.4.0以上版本
selfdestruct(address)
// 資料格式
struct Pledge {
    uint amount;
    address eth_address;
    bytes32 message;
}
// 修飾子等級
// function預設是public，state預設是internal
public - all
private - only this contract
internal - only this contract and contracts deriving from it
external - Cannot be accessed internally, only externally.
// mapping存key-value資料
mapping (address => uint) pendingWithdrawals;
// modifier重用檢查
modifier onlyOwner() {
    if (msg.sender != owner) throw;
    // 0.4.0之後這樣寫
    _;
}
function forceOwnerChange(address _newOwner) onlyOwner
{
    // just some example condition
    if (uint(owner) & 0 == 1)
        // This did not refund for Solidity
        // before version 0.4.0.
        return;
    // refund overpaid fees
}

其他語法請看官方文件

撰寫合約程式

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pragma solidity ^0.4.0;
contract test {
   function multiply(uint a) constant returns(uint d) {
      return a * 7;
   }
}

透過web3.js和ABI建立對應合約的js物件

ABI為Application Binary Interface
要讓其他程式語言看懂合約的接口所以需要該介面

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// web3常用格式，透過ABI產生可與合約互動的js物件
var contractClass = web3.eth.contract(<ABI>)
// 等下用此物件來部署此類合約
var browser_ballot_sol_testContract = web3.eth.contract([{"constant":true,"inputs":[{"name":"a","type":"uint256"}],"name":"multiply","outputs":[{"name":"d","type":"uint256"}],"payable":false,"type":"function"}])

部署合約與呼叫合約

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// 評估要花多少gas，通常會將此數字乘以1.2
web3.eth.estimateGas({data: '0x' + <bytecode>})
// 估計部署合約要花多少gas
web3.eth.estimateGas({data: '0x6060604052341561000f57600080fd5b5b60ab8061001e6000396000f30060606040526000357c0100000000000000000000000000000000000000000000000000000000900463ffffffff168063c6888fa114603d575b600080fd5b3415604757600080fd5b605b60048080359060200190919050506071565b6040518082815260200191505060405180910390f35b60006007820290505b9190505600a165627a7a72305820668369d5ec98bbd9e537eb377a779e58f87d27b4cb70f247366fafb14ceff1170029'})
98392
// 部署合約並產生合約的實例
var browser_ballot_sol_test = browser_ballot_sol_testContract.new(
   {
     // 用哪個地址去部署合約
     from: web3.eth.accounts[0], 
     // 合約程式碼的bytecode
     data: '0x6060604052341561000f57600080fd5b5b60ab8061001e6000396000f30060606040526000357c0100000000000000000000000000000000000000000000000000000000900463ffffffff168063c6888fa114603d575b600080fd5b3415604757600080fd5b605b60048080359060200190919050506071565b6040518082815260200191505060405180910390f35b60006007820290505b9190505600a165627a7a72305820668369d5ec98bbd9e537eb377a779e58f87d27b4cb70f247366fafb14ceff1170029', 
     // 要花的gas
     gas: '4700000'
   }, function (e, contract){
    // 當成功部署合約 顯示合約地址和部署合約的交易
    console.log(e, contract);
    if (typeof contract.address !== 'undefined') {
         console.log('Contract mined! address: ' + contract.address + ' transactionHash: ' + contract.transactionHash);
    }
 })
 
Contract mined! address: 0x2ff5f980d80cb37a5cd92678157ed49b06ef324f transactionHash: 0x0b5ba1bbdc28dddaa6b0b0207e9c72576c8c10b9db9b49b680791a33a4ab0bc7
eth.getTransaction("0x0b5ba1bbdc28dddaa6b0b0207e9c72576c8c10b9db9b49b680791a33a4ab0bc7")
{
  blockHash: "0xd139f77cba988b25ae7f10c12138b28e6630808259b86f290540bf7d80cbd10d",
  blockNumber: 858,
  from: "0x4560eb5a01478cbfa1390a4134cd752d99746266",
  gas: 4700000,
  gasPrice: 0,
  hash: "0x0b5ba1bbdc28dddaa6b0b0207e9c72576c8c10b9db9b49b680791a33a4ab0bc7",
  input: "0x6060604052341561000f57600080fd5b5b60ab8061001e6000396000f30060606040526000357c0100000000000000000000000000000000000000000000000000000000900463ffffffff168063c6888fa114603d575b600080fd5b3415604757600080fd5b605b60048080359060200190919050506071565b6040518082815260200191505060405180910390f35b60006007820290505b9190505600a165627a7a72305820668369d5ec98bbd9e537eb377a779e58f87d27b4cb70f247366fafb14ceff1170029",
  nonce: 1,
  r: "0x47f9359d20cded498ef3719390e4fbfe654f6438fbec71c397b29c70e8224f0d",
  s: "0x4cf4a110964044afd7de6bc3d1905f90583013d9948ed37736ebdc99b894c63d",
  to: null,
  transactionIndex: 0,
  v: "0xa95",
  value: 0
}
// 從js程式其他地方建立此合約地址的實例(意圖查看或改變此合約地址的state)
var contract = web3.eth.contract(<ABI>).at(<contract address>)
var contract = web3.eth.contract([{"constant":true,"inputs":[{"name":"a","type":"uint256"}],"name":"multiply","outputs":[{"name":"d","type":"uint256"}],"payable":false,"type":"function"}]).at("0x2ff5f980d80cb37a5cd92678157ed49b06ef324f")
// 與合約互動
browser_ballot_sol_test.multiply(7)
49 // 與合約互動的結果，呼叫合約的constant方法 不會在鏈上產生交易，不用等挖礦，也沒有改變state(不是合約的成員變數)，純粹回傳某個值
contract.multiply(15)
105

區塊鏈系統的好處是
所有跟此節點同步區塊的節點，都可以跟此合約地址的合約互動與透過介面操作該合約的state
形成一個網路，發展更多應用

meetup的合約教學

更複雜的合約案例 - 募款

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pragma solidity ^0.4.0;
contract smartSponsor {
  address public owner;
  address public benefactor;
  bool public refunded;
  bool public complete;
  uint public numPledges;
  struct Pledge {
    uint amount;
    address eth_address;
    bytes32 message;
  }
  mapping(uint => Pledge) public pledges;
  // constructor
  function smartSponsor(address _benefactor) {
    owner = msg.sender;
    numPledges = 0;
    refunded = false;
    complete = false;
    benefactor = _benefactor;
  }
  // add a new pledge
  function pledge(bytes32 _message) payable {
    if (msg.value == 0 || complete || refunded) revert();
    pledges[numPledges] = Pledge(msg.value, msg.sender, _message);
    numPledges++;
  }
  function getPot() constant returns (uint) {
    return this.balance;
  }
  // refund the backers
  function refund() {
    if (msg.sender != owner || complete || refunded) revert();
    for (uint i = 0; i < numPledges; ++i) {
      pledges[i].eth_address.transfer(pledges[i].amount);
    }
    refunded = true;
    complete = true;
  }
  // send funds to the contract benefactor
  function drawdown() {
    if (msg.sender != owner || complete || refunded) revert();
    benefactor.transfer(this.balance);
    complete = true;
  }
}

原文

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