Solidity

在上一篇文章中，我们可以看到 pragma solidity 0.4.9;,

这里的Solidity，就是以太坊智能合约的核心语言Solidity，也是本教程的重点。

Solidity是什么？

Solidity是以太坊智能合约的编程语言，通过编译&部署智能合约，可以实现智能合约的Create、执行和查看，从而实现某些商业应用。

几个简单的Solidity例子

通过以下几个智能合约，我们可以将一些商业应用很好的区块链化，从而实现去中介、去信任、高度透明的商业模型。

在之后的整个教程中，我们会逐步解析Solidity编程，帮助大家快速掌握Solidity这门语言，并且将区块链落地到前端Web页面上

I 实现1+2+3+..+n的求和功能

pragma solidity 0.4.9;
contract Demo1 {/*计算从1到N的求和*/function f(uint n) returns (uint sum) {if (n == 0) throw; uint result = 0;for (uint i=0; i<=n; i++) {result +=i;}return result;}
}

II 实现一个代币功能，并自带挖矿和转移代币的功能。

pragma solidity ^0.4.0;contract Coin {// The keyword "public" makes those variables// readable from outside.address public minter;mapping (address => uint) public balances;// Events allow light clients to react on// changes efficiently.event Sent(address from, address to, uint amount);// This is the constructor whose code is// run only when the contract is created.function Coin() {minter = msg.sender;}function mint(address receiver, uint amount) {if (msg.sender != minter) return;balances[receiver] += amount;}function send(address receiver, uint amount) {if (balances[msg.sender] < amount) return;balances[msg.sender] -= amount;balances[receiver] += amount;Sent(msg.sender, receiver, amount);}
}

III 实现一个众筹的智能合约，各个用户可以筹款、筹款成功可以将所得转让给受益人，每个参与众筹者可以获得代币。

pragma solidity ^0.4.2;
contract token { function transfer(address receiver, uint amount){  } }contract Crowdsale4 {address public beneficiary;uint public fundingGoal;uint public amountRaised;uint public deadline;uint public price;token public tokenReward;mapping(address => uint256) public balanceOf;bool public fundingGoalReached = false;event GoalReached(address beneficiary, uint amountRaised);event FundTransfer(address backer, uint amount, bool isContribution);bool public crowdsaleClosed = false;/* data structure to hold information about campaign contributors *//*  at initialization, setup the owner */function Crowdsale4 (address ifSuccessfulSendTo,uint fundingGoalInEthers,uint durationInMinutes,uint etherCostOfEachToken,token addressOfTokenUsedAsReward) {beneficiary = ifSuccessfulSendTo;fundingGoal = fundingGoalInEthers * 1 ether;deadline = now + durationInMinutes * 1 minutes;price = etherCostOfEachToken * 1 ether;tokenReward = token(addressOfTokenUsedAsReward);}/* The function without name is the default function that is called whenever anyone sends funds to a contract */function () payable {if (crowdsaleClosed) throw;uint amount = msg.value;balanceOf[msg.sender] += amount;amountRaised += amount;tokenReward.transfer(msg.sender, amount / price);FundTransfer(msg.sender, amount, true);}modifier afterDeadline() { if (now >= deadline) _; }/* checks if the goal or time limit has been reached and ends the campaign */function checkGoalReached() afterDeadline {if (amountRaised >= fundingGoal){fundingGoalReached = true;GoalReached(beneficiary, amountRaised);}crowdsaleClosed = true;}function safeWithdrawal() afterDeadline {if (!fundingGoalReached) {uint amount = balanceOf[msg.sender];balanceOf[msg.sender] = 0;if (amount > 0) {if (msg.sender.send(amount)) {FundTransfer(msg.sender, amount, false);} else {balanceOf[msg.sender] = amount;}}}if (fundingGoalReached && beneficiary == msg.sender) {if (beneficiary.send(amountRaised)) {FundTransfer(beneficiary, amountRaised, false);} else {//If we fail to send the funds to beneficiary, unlock funders balancefundingGoalReached = false;}}}
}

Solidity的简介就到此为止了，后面我们会具体解析这些合约的奥秘

前面说过，智能合约是部署在以太坊的网络上的，那么如何搭建一个以太坊网络呢，就需要官方提供的工具Geth了。下一章会详细说明。

原文地址： http://www.ethchinese.com/?p=630

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