智能合约---实现阶乘

一、环境：
1.Linux环境
2. 安装Ubuntu 16.04.
Ubuntu 16: Run “Software & Update”, for “downloaded from” choose sohu.com etc. as the source.
Passwd for ethtest is test.

3. install golang

• in a terminal window, run “sudo apt-get update”
• run “sudo apt-get install golang”

4. 下载geth源文件（https://github.com/ethereum/go-ethereum）
   unzip go-ethereum-master.zip
   (or git clone https://github.com/ethereum/go-ethereum)
   进入go-ethereum-master目录，编译go-ethereum:
   cd go-ethereum-master
   make
   将build/bin/geth拷贝到/usr/bin目录下:
   sudo cp build/bin/geth /usr/bin

5. 安装智能合约编译器solc

   sudo add-apt-repository ppa:ethereum/ethereum

sudo apt-get update

sudo apt-get install solc

which solc
二：
运行简单的智能合约(实现阶乘运算)
1.合约的内容：
contract Factorial{
function Compute(uint amount) public returns (uint){
uint output=1;
while(amount!=0){
output=outputamount;
amount–;
}
return (output);}}
2.打开命令终端输入：
~$ geth --rpc --rpccorsdomain "" --nodiscover console --dev.period 1
进入geth命令界面

3.第一次进入输入

eth.accounts

命令显示为[]，
即没有账户(有默认账户则不需要创建)。
首先创建一个账户：

personal.newAccount(“gyh”)

其中gyh为用户的密码

eth.getBalance(eth.accounts[0])

查看第一个账户的余额
如果为0输入

miner.start()

开始挖矿

miner.stop()

停止，再次查询余额会发现增多说明挖矿成功！

4.部署合约输入

abi==[{“constant”:false,“inputs”:[{“name”:“amount”,“type”:“uint256”}],“name”:“Compute”,“outputs”:[{“name”:"",“type”:“uint256”}],“payable”:false,“stateMutability”:“nonpayable”,“type”:“function”}]

其中标记部分的获得首先进入https://remix.ethereum.org
将第一步合约内容的代码输入之后Compile->Details



代码在第一行的中括号中

MyContract=eth.contract(abi)

>mycontract=MyContract.new(
{
from: web3.eth.accounts[0],
data: ‘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’,
gas: ‘4700000’
}, function (e, contract){
console.log(e, contract);
if (typeof contract.address !== ‘undefined’) {
console.log('Contract mined! address: ’ + contract.address + ’ transactionHash: ’ + contract.transactionHash);
}
})

标记部分用相同的方法获得

在此处提示了一个error 解决办法是将账户解锁：

personal.unlockAccount([eth.accounts[0])

密码是gyh
再次创建一次合约

mycontract=MyContract.new(
{
from: web3.eth.accounts[0],
data: ‘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’,
gas: ‘4700000’
}, function (e, contract){
console.log(e, contract);
if (typeof contract.address !== ‘undefined’) {
console.log('Contract mined! address: ’ + contract.address + ’ transactionHash: ’ + contract.transactionHash);
}
})

测试合约是否部署正确

txpool.status

若pending是0则部署失败；

miner.start()

开始挖矿

miner.stop()
txpool.status

这时显示pending 为0则成功

5、调用合约：

Factorial=MyContract.at(mycontract.address)

address一定是一个地址值，不存在或为null则错误

Factorial.Compute.call(3) 显示3阶乘的结果为6

试验完成！