pragma solidity ^0.4.4;

contract funder{

    //0xca35b7d915458ef540ade6068dfe2f44e8fa733c
    //0x14723a09acff6d2a60dcdf7aa4aff308fddc160c :10
    //0x583031d1113ad414f02576bd6afabfb302140225 :20

    struct Funder{
        address addr;
        uint amount;
    }

    struct Campaign{
        address beneficiary; //受益人
 

        uint fundingGoal; //集資目標
        uint numFunders;  //出資人數
        uint mount;       //已集資數
        mapping(uint => Funder) Funders; //按照索引存儲出資人信息
    }

    uint numCampaigns;
    mapping(uint => Campaign) public Campaigns;  //按照索引存儲每個受益人的狀態

    //向指定受益人出資一定數量的錢
    //function newCampaign(address beneficiary,uint goal) public returns(uint campaignID){
 

    //function newCampaign(address beneficiary,uint goal) public{ //DeclarationError: Undeclared identifier__campaignID
    function newCampaign(address beneficiary,uint goal) public{
        //var campaignID = numCampaigns++;
        //Campaigns[campaignID] = Campaign(beneficiary,goal,0,0);

        Campaigns[numCampaigns] 
 
= Campaign(beneficiary,goal,0,0);
        numCampaigns ++;

    }

    function contribute(uint campaignID) public payable{
        Campaign storage c = Campaigns[campaignID];  //每個受益人的狀態
        c.Funders[c.numFunders++] = Funder({addr:msg.sender,amount:msg.value});
        //Funder({addr:msg.sender,amount:msg.value}) 當前轉賬人的地址,和轉賬金額
        //c.numFunders++ 統計向當前受益人轉賬的人數
        // 0 => 轉賬地址
        c.mount += msg.value; //當前受益人的總受益
        c.beneficiary.transfer(msg.value);//向受益人的地址轉入ethtereum
    }

    function checkGoalReached(uint campaignID) public constant returns(bool reached){
        Campaign storage c = Campaigns[campaignID];
        if(c.mount < c.fundingGoal){
            return false;
        }
        return true;
    }
}

遇到的問題:
1.受益人可以相同

ethereum(以太坊)(十二)--集資(構造函數/映射)