# 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/](https://remix.ethereum.org/#version=soljson-v0.4.17+commit.bdeb9e52.js)
>
> 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

![](/files/-M0u4O14a-mCe3_iIhMl)

```
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)\
![](/files/-M0u4SCSf1M2qXKpiE61)\
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)

```javascript
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


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