基于mcat开发智能合约应用（三）编码自动化与合约交互

#### 前言

上一节中演示了怎么通过手动去部署合约方法和调用合约方法，生产环境下部署合约可能只是一次性操作，但是与合约交互是一个高频操作，而且还需要夹杂其它的业务逻辑，这就需要编码来实现与合约交互。调用合约方法的过程，可以分为两类，一种是需要修改账本数据的，那么它必须是一笔交易，否则只在本地执行是没有实际意义的；另外一种是查询操作，比如查询合约的某个状态变量值，那么它是`constant`类型的，并不需要修改账本，那么这个调用只用在本地节点执行即可，无需消耗gas，也不需要被矿工打包，可即时返回结果。

#### 使用php编码与合约进行交互

`mcat`提供了一个serve的功能，它的作用是起一个本地的server，监听指定的端口（mcat.yaml里面配置），把需要调用的合约方法和参数传进去，它会帮你计算出transaction data字段的字节码。

启动mcat server

```

luren5@ubuntu:~$ mcat serve

server has been started, listening 50729

```

编写php代码与合约交互

```

class Ballot {

// 投票发起人

public $chairperson;

//

function giveRightToVote($voter_addr, $voter_name) {

$data = array(

'method'=> 'TxData.Detail',

'params'=> array(array(

"Contract" => "Ballot",

"Function" => "giveRightToVote",

"Params" => sprintf("%s&%s", $voter_addr, $voter_name)

)),

'id'=> 1

);

$txDatail = getDataDetail($data);

$txDatail = json_decode($txDatail, true);

$gas = $txDatail["Gas"];

$bin = $txDatail["Bin"];

$txHash = sendTransaction($gas, $bin);

echo sprintf("Success in call giveRightToVote with params (%s, %s), the tx hash is %s \r\n", $voter_addr, $voter_name, $txHash);

}

}

// utils

function getDataDetail($data) {

$url = "http://localhost:50729"; // 这里是mcat server的信息

$r = sendPost($url, $data);

$r = json_decode($r, true);

if(empty($r["error"])) {

return $r["result"];

} else {

echo "Failed to get the tx data detail, err: ", $r["error"];

exit();

}

}

function sendPost($url, $data) {

$ch = curl_init();

curl_setopt($ch, CURLOPT_URL, $url);

curl_setopt($ch, CURLOPT_POST, 1);

curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json'));

curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($data));

$res = curl_exec($ch);

return $res;

}

function sendTransaction($gas, $bin) {

unlock(); // 发交易之前需要对默认账户进行解锁

$data = array(

"id" => 1,

"method" => "eth_sendTransaction",

"params" => array(array(

"from" => "0x0b9498ca74cd7814fba0c25e2a441c1d5867946a", // 这里是默认发交易的地址，也是合约的创建者

"to" => "0xd2548bb40fe57aa9e66aeafbc1f6a44c9d8b9532", // 这里是合约账户地址

"gas" => $gas,

"data" => $bin

))

);

$url = "http://localhost:8090";

$r = sendPost($url, $data);

$r = json_decode($r, true);

if(!empty($r["result"])) {

return $r["result"] ;

} else {

echo "Failed to send transaction";

exit();

}

}

function unlock() {

$default_account = "0x0b9498ca74cd7814fba0c25e2a441c1d5867946a";

$default_account_password = "123456";

$data = array(

"method" => "personal_unlockAccount",

"params" => array(

$default_account, $default_account_password,

),

"id" => 1

);

$url = "http://localhost:8090";

$r = sendPost($url, $data);

$r = json_decode($r, true);

if ($r["result"] != true) {

echo "Failed to unlock the default account";

exit();

}

}

$b = new Ballot();

$b->giveRightToVote("0xab4c1e40f28f00c8c79d77c6079437bbd5ab6cd1", "voter3");

```

执行

```

luren5@ubuntu:~$ php test.php

Success in call giveRightToVote with params (0xab4c1e40f28f00c8c79d77c6079437bbd5ab6cd1, voter3), the tx hash is 0x2ea6103b38e819ca72cd7ca0b2c9ccbae92828d1140913d2cf63c3593845e26d

```

等待交易被打包后，这个调用授权方法的操作即成功了，调用合约其它的方法也是类似

原文地址： https://zhuanlan.zhihu.com/p/29786430