12.12大宗商品区块链系统购买

// 示例代码展示如何通过智能合约进行大宗商品交易
pragma solidity ^0.8.0;

contract CommodityTrade {
    struct Trade {
        address buyer;
        address seller;
        uint256 quantity;
        uint256 price;
        bool completed;
    }

    mapping(uint256 => Trade) public trades;
    uint256 public tradeCount;

    event TradeCreated(uint256 indexed id, address buyer, address seller, uint256 quantity, uint256 price);
    event TradeCompleted(uint256 indexed id);

    function createTrade(address _buyer, uint256 _quantity, uint256 _price) public {
        tradeCount++;
        trades[tradeCount] = Trade(_buyer, msg.sender, _quantity, _price, false);
        emit TradeCreated(tradeCount, _buyer, msg.sender, _quantity, _price);
    }

    function completeTrade(uint256 _id) public {
        Trade storage trade = trades[_id];
        require(trade.buyer == msg.sender, "Only buyer can complete the trade");
        require(!trade.completed, "Trade already completed");
        // 执行交易逻辑，如转移资产等
        trade.completed = true;
        emit TradeCompleted(_id);
    }
}