[區塊鏈報明牌]Day 20 Ethereum(3)-DAO

2018鐵人賽區塊鏈

willyc20

2018-01-07 14:51:35

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什麼是DAO

DAO(Distributed Autonomous Organization)翻譯就是去中心化的自治組織。

一樣先來看看wiki的描述:

The DAO had an objective to provide a new decentralized business model for organizing both commercial and non-profit enterprises. It was instantiated on the Ethereum blockchain, and had no conventional management structure or board of directors. The code of the DAO is open-source.

果然是霧裡雲裡的形容，以Lawrence Lessig教授的話"code is law."來形容可能較為貼切。簡單來看在Ethereum中的DAO是這樣的，在智能合約中寫代碼定義一些規則，這些規則就是想要建構的DAO組織的規則，然後對這個組織的運作都是經由智能合約來執行的。

思考順序大概是這樣:

1.區塊鏈上的資料是不可竄改的，所以不需要人維持運作來確保公性力。

2.區塊鏈上執行智能合約來定義規則(其實就是把code放到區塊鏈裡跑)。

3.組織中的人進行決策和討論都要經由Ethereum，自然必須符合智能合約定義的標準才能運作。

此外考慮到乙太幣本身的價值以及上面運作的那些代幣的價值，以這種模式進行金流方面的操作會是一件很可行的事情。

The Blockchain Congress

為了了解DAO的運作模式，我們實際使用ethereum的智能合約範例，今天要做的事是通過這個DAO組織進行投票，以此把day 19的lottery token傳給其他地址。

先來看看今天的操作流程中會用到的程式碼:

提案，其實就是把提案要描述的變數填一填:

/**
 * Add Proposal
 *
 * Propose to send `weiAmount / 1e18` ether to `beneficiary` for `jobDescription`. `transactionBytecode ? Contains : Does not contain` code.
 *
 * @param beneficiary who to send the ether to
 * @param weiAmount amount of ether to send, in wei
 * @param jobDescription Description of job
 * @param transactionBytecode bytecode of transaction
 */
function newProposal(
    address beneficiary,
    uint weiAmount,
    string jobDescription,
    bytes transactionBytecode
)
    onlyMembers public
    returns (uint proposalID)
{
    proposalID = proposals.length++;
    Proposal storage p = proposals[proposalID];
    p.recipient = beneficiary;
    p.amount = weiAmount;
    p.description = jobDescription;
    p.proposalHash = keccak256(beneficiary, weiAmount, transactionBytecode);
    p.votingDeadline = now + debatingPeriodInMinutes * 1 minutes;
    p.executed = false;
    p.proposalPassed = false;
    p.numberOfVotes = 0;
    ProposalAdded(proposalID, beneficiary, weiAmount, jobDescription);
    numProposals = proposalID+1;

    return proposalID;
}

投票，p.currentResult加加減減:

/**
 * Log a vote for a proposal
 *
 * Vote `supportsProposal? in support of : against` proposal #`proposalNumber`
 *
 * @param proposalNumber number of proposal
 * @param supportsProposal either in favor or against it
 * @param justificationText optional justification text
 */
function vote(
    uint proposalNumber,
    bool supportsProposal,
    string justificationText
)
    onlyMembers public
    returns (uint voteID)
{
    Proposal storage p = proposals[proposalNumber];         // Get the proposal
    require(!p.voted[msg.sender]);         // If has already voted, cancel
    p.voted[msg.sender] = true;                     // Set this voter as having voted
    p.numberOfVotes++;                              // Increase the number of votes
    if (supportsProposal) {                         // If they support the proposal
        p.currentResult++;                          // Increase score
    } else {                                        // If they don't
        p.currentResult--;                          // Decrease the score
    }

    // Create a log of this event
    Voted(proposalNumber,  supportsProposal, msg.sender, justificationText);
    return p.numberOfVotes;
}

如果得票數高於minimumQuorum就同意:

/**
 * Finish vote
 *
 * Count the votes proposal #`proposalNumber` and execute it if approved
 *
 * @param proposalNumber proposal number
 * @param transactionBytecode optional: if the transaction contained a bytecode, you need to send it
 */
function executeProposal(uint proposalNumber, bytes transactionBytecode) public {
    Proposal storage p = proposals[proposalNumber];

    require(now > p.votingDeadline                                            // If it is past the voting deadline
        && !p.executed                                                         // and it has not already been executed
        && p.proposalHash == keccak256(p.recipient, p.amount, transactionBytecode)  // and the supplied code matches the proposal
        && p.numberOfVotes >= minimumQuorum);                                  // and a minimum quorum has been reached...

    // ...then execute result

    if (p.currentResult > majorityMargin) {
        // Proposal passed; execute the transaction

        p.executed = true; // Avoid recursive calling
        require(p.recipient.call.value(p.amount)(transactionBytecode));

        p.proposalPassed = true;
    } else {
        // Proposal failed
        p.proposalPassed = false;
    }

    // Fire Events
    ProposalTallied(proposalNumber, p.currentResult, p.numberOfVotes, p.proposalPassed);
}

可以看到其實智能合約執行的code一般邏輯上都不難，更重要的是檢查錯誤，畢竟合約錯誤就好比法律有漏洞，後果是很嚴重的。