ethereum(Dapp)

Dapp

我們可以讓網頁使用web3.js連線到我們本地端的IPC 或 RPC 來讀取資料顯示到網頁，而mainnet和testnet都一樣，因為都是從geth 讀取同步區塊鏈後用本機的IPC或RPC把資料以類似API方式傳給網頁

實作

我們一樣先執行剛才的節點

geth  --ipcdisable --rpc --rpcport 8104 --datadir "./privatechain/01" --networkid 123 --rpccorsdomain="*" --rpcapi="db,eth,net,web3,personal" --nodiscover --port=30310 console

下面是我們這次要加入的token合約

contract token { 
    mapping (address => uint) public coinBalanceOf;
    event CoinTransfer(address sender, address receiver, uint amount);

  /* Initializes contract with initial supply tokens to the creator of the contract */
  function token(uint supply) {
        coinBalanceOf[msg.sender] = supply;
    }

  /* Very simple trade function */
    function sendCoin(address receiver, uint amount) returns(bool sufficient) {
        if (coinBalanceOf[msg.sender] < amount) return false;
        coinBalanceOf[msg.sender] -= amount;
        coinBalanceOf[receiver] += amount;
        CoinTransfer(msg.sender, receiver, amount);
        return true;
    }
}

var tokenSource = ' contract token { mapping (address => uint) public coinBalanceOf; event CoinTransfer(address sender, address receiver, uint amount); /* Initializes contract with initial supply tokens to the creator of the contract */ function token(uint supply) { coinBalanceOf[msg.sender] = supply; } /* Very simple trade function */ function sendCoin(address receiver, uint amount) returns(bool sufficient) { if (coinBalanceOf[msg.sender] < amount) return false; coinBalanceOf[msg.sender] -= amount; coinBalanceOf[receiver] += amount; CoinTransfer(msg.sender, receiver, amount); return true; } }'

把上面的部分複製到我們的geth console 中

然後進行編譯

var tokenCompiled= web3.eth.compile.solidity(tokenSource)

如出現 Error: The method eth_compileSolidity does not exist/is not available

代表solidity版本 > 1.6 需要用線上編譯 https://remix.ethereum.org/

然後把網頁上Deploy部分貼上 之後直接跳到本章節的步驟三

之後試著輸入以下，即可看到剛才compile後的部分

tokenCompiled["<stdin>:token"].info.abiDefinition //查看我們合約的API

[{
    constant: false,
    inputs: [{
        name: "receiver",
        type: "address"
    }, {
        name: "amount",
        type: "uint256"
    }],
    name: "sendCoin",
    outputs: [{
        name: "sufficient",
        type: "bool"
    }],
    payable: false,
    type: "function"
}, {
    constant: true,
    inputs: [{
        name: "",
        type: "address"
    }],
    name: "coinBalanceOf",
    outputs: [{
        name: "",
        type: "uint256"
    }],
    payable: false,
    type: "function"
}, {
    inputs: [{
        name: "supply",
        type: "uint256"
    }],
    payable: false,
    type: "constructor"
}, {
    anonymous: false,
    inputs: [{
        indexed: false,
        name: "sender",
        type: "address"
    }, {
        indexed: false,
        name: "receiver",
        type: "address"
    }, {
        indexed: false,
        name: "amount",
        type: "uint256"
    }],
    name: "CoinTransfer",
    type: "event"
}]

設定帳戶

然後我們先用以下指令，確定我們鏈上有帳號(也可查看keystore資料夾)

web3.eth.accounts

如果沒有可打開Mist新增或輸入personal.newAccount()

Mac

/Applications/Ethereum\ Wallet.app/Contents/MacOS/Ethereum\ Wallet --rpc http://localhost:8104

Windows

先將以下加入環境變數

C:\Program Files\Mist

然後開啟terminal輸入

mist --rpc http://localhost:8104

之後輸入以下綁定帳號到節點

web3.miner.setEtherbase("輸入地址")

然後輸入以下來解鎖帳號(讓帳號可以交易)

personal.unlockAccount(web3.eth.accounts[0], "輸入此帳號的password")

接著把我們剛才的合約實例化，並部署

如果是solidity版本大於1.6用剛才的線上編譯器 然後點選deploy之後複製

然後先在terminal輸入 supply = 10000; 然後貼上剛才複製的部分

var supply = 10000;
var tokenContract = web3.eth.contract(tokenCompiled["<stdin>:token"].info.abiDefinition);
var token = tokenContract.new(
  supply,
  {
    from:web3.eth.accounts[0], 
    data:tokenCompiled["<stdin>:token"].code, 
    gas: 1000000
  }, function(e, contract){
      if(e){console.log(e); }
    if(!e) {
      if(!contract.address) {
        console.log("Contract transaction send: TransactionHash: " + contract.transactionHash + " waiting to be mined...");

      } else {
        console.log("Contract mined! Address: " + contract.address);
        console.log(contract);
      }

    }
})

正常的話會出現如下

I0215 20:34:36.263099 internal/ethapi/api.go:1074] Tx(0x09d25084b1d471a48c371bb98f54dde88b59af24348a7b2b29a09bc91c7c9727) created: 0x14067c5707025c4dabba49949c0c166070b4f5c9
Contract transaction send: TransactionHash: 0x09d25084b1d471a48c371bb98f54dde88b59af24348a7b2b29a09bc91c7c9727 waiting to be mined...

再來為了要把合約加入Blockchain我們要用挖礦方式產生新區塊

因為在私鏈所以我們要自己挖

miner.start(1)

產生完Dag後接著挖到contract後可以stop

miner.stop()

然後就可以輸入以下

browser_ballot_sol_token.coinBalanceOf(web3.eth.accounts[0])

即會出現餘額

監聽

在console貼上如下，因為我們剛contract有寫event

var event = browser_ballot_sol_token.CoinTransfer({}, '', function(error, result){
  if (!error)
    console.log("Coin transfer: " + result.args.amount + " tokens were sent. Balances now are as following: \n Sender:\t" + result.args.sender + " \t" + token.coinBalanceOf.call(result.args.sender) + " tokens \n Receiver:\t" + result.args.receiver + " \t" + token.coinBalanceOf.call(result.args.receiver) + " tokens" )
});

之後有人使用這個合約都會有通知

再來我們要試著轉一些token從帳號0給帳號1 (如果沒有一樣用錢包新增)

先解鎖兩個帳號

personal.unlockAccount(web3.eth.accounts[1], "輸入password")

personal.unlockAccount(web3.eth.accounts[0], "輸入password")

查看餘額

browser_ballot_sol_token.coinBalanceOf(web3.eth.accounts[1])

轉帳

browser_ballot_sol_token.sendCoin.sendTransaction(web3.eth.accounts[1], 1000, {from: web3.eth.accounts[0]})

成功會console如下

I0215 20:47:15.628190 internal/ethapi/api.go:1076] Tx(0x0bf7ec2dc727fb9d9943aeabca86c92616f178691f96667db251c16370b0d367) to: 0x14067c5707025c4dabba49949c0c166070b4f5c9

再來一樣要先挖礦

miner.start(1)

即可看到剛才的交易紀錄(即為我們剛才寫的event) 然後輸入如下

browser_ballot_sol_token.coinBalanceOf(web3.eth.accounts[1])

即可看到1000，即為剛才轉過去的

2.把剛才的合約部署到其他節點

為了使得其他人可以運行你的智能合約，你需要兩個資訊： 1.智能合約地址Address 2.智能合約ABI（Application Binary Interface），ABI其實就是一個有序的用戶手冊，描述了所有方法的名字和如何調用它們。

我們可以使用如下獲得其ABI和智能合約地址:

如solidity版本 > 1.6 一樣使用Remix進行合約ABI查看

點選Details 然後選 interface

查看地址 : 輸入browser_ballot_sol_token.address

browser_ballot_sol_token . address

執行另一個節點

geth  --ipcdisable --rpc --rpcport 8105 --datadir "./privatechain/02" --networkid 123 --rpccorsdomain="*" --rpcapi="db,eth,net,web3,personal" --nodiscover --port=30311 console

接著我們到另一個節點的console輸入如下，把ABI與Address更改為剛讀取出來的值(建議開一個檔案修改，之後再貼到console，因為code多console不好修改)

var token = web3.eth.contract(ABI).at(Address);

接著每個節點有自己的帳戶，所以我們先取的節點一的地址

 web3.eth.accounts[1]

然後到另一個terminal把地址貼上到框框中

token.coinBalanceOf("0x7d92564bf8e41e093f265da1532ef4143f398461")

如發現金額仍然是0，但應該要是1000，我們可以跟另一個節點做區塊鏈同步即可解決

所以先把第一個節點加入，步驟如下

於第一個節點輸入admin.nodeInfo => 複製enode url=> 第二個節點輸入admin.addPeer("剛才複製的enode url")

之後再到第二個節點輸入以下，即可同步區塊

miner.start(1)

記得先解鎖
web3.miner.setEtherbase(web3.eth.accounts[0]);
personal.unlockAccount(web3.eth.accounts[0], "輸入此帳號的password");

此時第二個節點也會出現相同金額了!

之後有新節點加入都是類似輸入如下，並且addPeer

var token = web3.eth.contract([{
    constant: false,
    inputs: [{
        name: "receiver",
        type: "address"
    }, {
        name: "amount",
        type: "uint256"
    }],
    name: "sendCoin",
    outputs: [{
        name: "sufficient",
        type: "bool"
    }],
    payable: false,
    type: "function"
}, {
    constant: true,
    inputs: [{
        name: "",
        type: "address"
    }],
    name: "coinBalanceOf",
    outputs: [{
        name: "",
        type: "uint256"
    }],
    payable: false,
    type: "function"
}, {
    inputs: [{
        name: "supply",
        type: "uint256"
    }],
    payable: false,
    type: "constructor"
}, {
    anonymous: false,
    inputs: [{
        indexed: false,
        name: "sender",
        type: "address"
    }, {
        indexed: false,
        name: "receiver",
        type: "address"
    }, {
        indexed: false,
        name: "amount",
        type: "uint256"
    }],
    name: "CoinTransfer",
    type: "event"
}]).at("0x14067c5707025c4dabba49949c0c166070b4f5c9");

接著我們看下一章來做成一個網頁