区块链应用设计与开发-任务七课后题答案

任务七课后题答案操作题1.跟随本任务完成货运追踪智能合约的开发并成功调用运行。//SPDX-License-Identifier:MITpragmasolidity^0.8.0;contractBuySell{structItem{uintItemId;stringname;uintamount;}structBuyer{uintBuyerId;addressBuyerAddress;boolisBuyer;uintOrderCount;//totalnumbeoforderplaced}structOrder{uintOrderId;uintBuyerId;uintItemId;uintamount;boolShipped;//canonlybechangedbysellerboolFinished;//canonlybechangedbybuyer}//moretodo://seperatefinishedandunfinishedorders//buyerscanplaceorderwithitemname//theaddressdeploysthecontractwillbethesellerconstructor(){Seller=msg.sender;}addresspublicSeller;//createlistofitems,buyers,abdordersItem[]privateitems;Buyer[]privatebuyers;Order[]privateorders;//sellercreateitemwithid,name,amountfunctioncreateItem(stringmemory_name,uint_quantity)public{//require(msg.sender==Seller,"OnlySellercanadditem.");items.push(Item(items.length,_name,_quantity));}//sellerregisteraaddressasbuyerfunctionregBuyer(address_address)public{require(msg.sender==Seller,"OnlySellercanaddbuyer.");buyers.push(Buyer(buyers.length,_address,true,0));}//showthelistofitems/buyers/ordersfunctiongetAllItems()publicviewreturns(Item[]memory){returnitems;}functiongetAllBuyers()publicviewreturns(Buyer[]memory){returnbuyers;}functiongetAllOrders()publicviewreturns(Order[]memory){returnorders;}functiongetOrderStatus(uint_id)publicviewreturns(Ordermemory){returnorders[_id];}//manageitemamountfunctionupdateItemQuantity(uint_id,uint_newQuantity)public{require(_id<items.length,"Itemdoesnotexist.");require(msg.sender==Seller,"OnlySellercanmanageitems");items[_id].amount=_newQuantity;}functionincreaseItemQuantity(uint_id,uint_increaseBy)public{require(msg.sender==Seller,"OnlySellercanmanageitems");require(_id<items.length,"Itemdoesnotexist.");items[_id].amount+=_increaseBy;}functiondecreaseItemQuantity(uint_id,uint_decreaseBy)public{require(msg.sender==Seller,"OnlySellercanmanageitems");require(_id<items.length,"Itemdoesnotexist.");require(items[_id].amount>=_decreaseBy,"Quantitywouldbecomenegative.");items[_id].amount-=_decreaseBy;}//buyerorderspecificitemfunctioncreateOrder(uint_buyerId,uint_id,uint_quantity)public{require(_id<items.length,"Itemdoesnotexist.");require(_buyerId<buyers.length,"Userdoesnotexist.");require(msg.sender==buyers[_buyerId].BuyerAddress,"OnlyBuyercanplaceorder.");//decreaseItemQuantity(_id,_quantity);buyers[_buyerId].OrderCount+=1;orders.push(Order(orders.length,_buyerId,_id,_quantity,false,false));}//sellerchecktheorder,shiptheorderandmarktheorderasshippedfunctionshipOrder(uint_id)public{require(msg.sender==Seller,"OnlySellercanmodifyorders.");decreaseItemQuantity(orders[_id].ItemId,orders[_id].amount);orders[_id].Shipped=true;}//buyerrecievetheorder,marktheorderasfinished,tradefinishedfunctionrecieveOrder(uint_BuyerId,uint_OrderId)public{require(_BuyerId==orders[_OrderId].BuyerId,"Wronguser.");require(msg.sender==buyers[_BuyerId].BuyerAddress,"OnlyBuyercanfinishorder.");orders[_OrderId].Finished=true;}}2.对智能合约进行优化。//SPDX-License-Identifier:MITpragmasolidity^0.8.0;contractBuySell{//定义物品、买家和订单的结构体structItem{uintitemId;stringname;uintamount;}structBuyer{uintbuyerId;addressbuyerAddress;uintorderCount;//订单总数}structOrder{uintorderId;uintbuyerId;uintitemId;uintamount;boolshipped;//只能由卖家更改boolfinished;//只能由买家更改}addresspublicseller;//存储物品、买家和订单的数组Item[]privateitems;Buyer[]privatebuyers;Order[]privateorders;//映射检查地址是否注册为买家mapping(address=>bool)publicisBuyer;constructor(){seller=msg.sender;}//检查调用者是否为卖家的修饰符modifieronlySeller(){require(msg.sender==seller,"Onlysellercanperformthisaction.");_;}//检查调用者是否为注册买家的修饰符modifieronlyBuyer(uint_buyerId){require(isBuyer[msg.sender],"Onlyregisteredbuyerscanperformthisaction.");require(buyers[_buyerId].buyerAddress==msg.sender,"IncorrectbuyerID.");_;}//卖家创建新物品的函数functioncreateItem(stringmemory_name,uint_amount)publiconlySeller{items.push(Item(items.length,_name,_amount));}//卖家注册新买家的函数functionregisterBuyer(address_buyerAddress)publiconlySeller{require(!isBuyer[_buyerAddress],"Buyerisalreadyregistered.");buyers.push(Buyer(buyers.length,_buyerAddress,0));isBuyer[_buyerAddress]=true;}//获取所有物品列表的函数functiongetAllItems()publicviewreturns(Item[]memory){returnitems;}//获取所有买家列表的函数functiongetAllBuyers()publicviewreturns(Buyer[]memory){returnbuyers;}//获取所有订单列表的函数functiongetAllOrders()publicviewreturns(Order[]memory){returnorders;}//获取特定订单状态的函数functiongetOrderStatus(uint_orderId)publicviewreturns(Ordermemory){require(_orderId<orders.length,"Orderdoesnotexist.");returnorders[_orderId];}//卖家更新物品数量的函数functionupdateItemQuantity(uint_itemId,uint_newQuantity)publiconlySeller{require(_itemId<items.length,"Itemdoesnotexist.");items[_itemId].amount=_newQuantity;}//卖家增加物品数量的函数functionincreaseItemQuantity(uint_itemId,uint_increaseBy)publiconlySeller{require(_itemId<items.length,"Itemdoesnotexist.");items[_itemId].amount+=_increaseBy;}//卖家减少物品数量的函数functiondecreaseItemQuantity(uint_itemId,uint_decreaseBy)publiconlySeller{require(_itemId<items.length,"Itemdoesnotexist.");require(items[_itemId].amount>=_decreaseBy,"Quantitywouldbecomenegative.");items[_itemId].amount-=_decreaseBy;}//买家创建新订单的函数functioncreateOrder(uint_buyerId,uint_itemId,uint_amount)publiconlyBuyer(_buyerId){require(_itemId<items.length,"Itemdoesnotexist.");require(items[_itemId].amount>=_amount,"Insufficientitemquantity.");orders.push(Order(orders.length,_buyerId,_itemId,_amount,false,false));buyers[_buyerId].orderCount+=1;}//卖家发货的函数functionshipOrder(uint_orderId)publiconlySeller{require(_orderId<orders.length,"Orderdoesnotexist.");Orderstorageorder=orders[_orderId];require(!order.shipped,"Orderalreadyshipped.");decreaseItemQua