类内结构的c ++向量

Question

大家好，我正在从事一个名为库存调查员的学校项目。规格如下：

enter image description here

到目前为止，我已经创建了一个类，其中包含一个结构和该结构的向量。 到目前为止，我所做的只是让类显示结构只是为了知道它可以工作，但是当我编译它并运行它时，什么也没有发生。这是代码。原谅我犯的任何菜鸟错误，我对课程和向量都很陌生。提前谢谢你！

//Inventory Inquisitor.cpp
#include <iostream>
#include <string>
#include <cctype> //for toupper
#include <fstream>
#include <vector>
using namespace std;

class Inventory
{
  private:
  struct item
   {
  string Description = " ";
  double Quantity = 0;
  double Wholesalescost = 0;
  double Retailcost = 0;
  string Dateadded = " ";
   };
   vector<item> Inv;
public:
  void Display();

};

void Inventory::Display()
{ 

 Inv[0].Description = "english";
 Inv[0].Quantity = 1;
 Inv[0].Wholesalescost = 100;
 Inv[0].Retailcost = 200;
 Inv[0].Dateadded = "3/8/2018";
 cout << Inv[0].Description << endl;
 cout << Inv[0].Quantity << endl;
 cout << Inv[0].Wholesalescost << endl;
 cout << Inv[0].Retailcost << endl;
 cout << Inv[0].Dateadded << endl;
}

int main()
{
 Inventory inst1;

  inst1.Display();

 }

Answer 1

在访问它之前，你必须在向量中放入一些东西：

// Create an item
item i;
i.Description = "english";
i.Quantity = 1;
i.Wholesalescost = 100;
i.Retailcost = 200;
i.Dateadded = 3/8/2018;

// The vector is empty, size() == 0    
// Add it to the vector
Inv.push_back(i);
// Now the vector has 1 item, size() == 1

// Now you can print it
cout << Inv.at(0).Description << endl;
cout << Inv.at(0).Quantity << endl;
cout << Inv.at(0).Wholesalescost << endl;
cout << Inv.at(0).Retailcost << endl;
cout << Inv.at(0).Dateadded << endl;

根据您的任务，您很可能会更改为打印现有项目的功能。您将有另一个函数可以将项目添加到向量中。

void Inventory::Display(int index)
{ 
    // Print an item already in the vector
    if (index >= 0 && index < Inv.size()) {
        cout << Inv.at(index).Description << endl;
        cout << Inv.at(index).Quantity << endl;
        cout << Inv.at(index).Wholesalescost << endl;
        cout << Inv.at(index).Retailcost << endl;
        cout << Inv.at(index).Dateadded << endl;
    }
}