我如何計算有多少買家向我的智能合約提出請求並獲得了乙太幣

October 13, 2019

我正在使用工廠契約來銷售和購買商品。如何檢索有多少買家購買併計算出售商品賺取了多少乙太幣？這是我的原始碼。我是智能合約的新手

contract FactroyContract {
 address[] public contracts;
 address public lastContractAddresses;

 event newPurchaseContract (address contractAddress);

 function getContractcount() public view returns(uint ContracCount) 
 {
   return contracts.length;
 }

 function newPurchase(uint value, string memory bookName, string memory description, string memory imageHash, string memory privHash, string memory dataHash) 
   public 
   payable
   returns(address NewContract)
 {
   Purchase c = new Purchase(address(msg.sender), value, bookName, description, imageHash, privHash, dataHash);
   contracts.push(c);
   lastContractAddresses = address(c);
   emit newPurchaseContract(c);
   return c;
 }

 function seePurchase(uint pos) public view returns(address contractAddress)
 {
   return address(contracts[pos]);
 }
}

contract Purchase
{
 uint public price;
 address public seller;
 address[] public buyers;
 address public buyer;
 string public ipfsHash;
 string public preview;
 string public cover;
 string public name;
 string public text;

 constructor(address contractSeller, uint value, string memory bookName, string memory description, string memory imageHash, string memory privHash, string memory dataHash) public payable
 {
   seller = contractSeller;
   name = bookName; 
   text = description;
   cover = imageHash;
   preview = privHash;
   ipfsHash = dataHash;
   price = value * 1000000000000000000;
 }

 modifier condition(bool _condition) 
 {
   require(_condition);
   _;    
 }

 modifier onlyBuyer()
 {
   (msg.sender == buyer);
   _;
 }

 modifier onlySeller()
 {
   (msg.sender == seller);
   _;
 }

 event ItemReceived();

 function confrimReceived() public 
   condition(msg.value == price)
   payable
 {
   emit ItemReceived();

   buyer = msg.sender;
   seller.transfer(address(this).balance);
 }
 function getBuyerCount() public view returns(address buyerAddresses)
 {
   return buyers.length;
 }

 function getEtherCount() public view return(uint earnedEather)
 {
   return price+= msg.value;
 }
}

智能合約內部Purchase定義了買家總數和總收入的計數器，如下所示：
contract Purchase
{
 uint public totalBuyers = 0;
 uint public totalEarnings = 0;
 ...
}
然後，當確認購買時，適當增加這些計數器：
function confrimReceived() public 
 condition(msg.value == price)
 payable
{
 totalBuyers += 1;
 totalEarnings += price;
 ...
}
只要計數器是公開的，您就可以從其他智能合約或鏈下應用程序，甚至從Etherscan.io查詢它們。