将函数转换为成员函数？

Question

我是新来的，我在用C++编写的程序寻求帮助。

我想转换下列功能不在一个班，也没有在main（）为一类库存的公共职能的成员有没有参数和返回任何结果我的程序

void PrintInventory(vector<Item*> inventory); 
vector<Item*> AddItemToInventory(vector<Item*> inventory); 
vector<Item*> UpdateItemQtyInInventory(vector<Item*> inventory); 
vector<Item*> RemoveItemFromInventory(vector<Item*> inventory); 

的。

我一直对4天了，只是想不通，我应该如何改变这些功能是无效的，并具有不破坏整个程序没有参数...

如果我去完全按指令说什么这是使空/无参数出的四大功能，我会得到这样的：

class Inventory 
{ 
public: 
    void PrintInventory() {} 
    void AddItemToInventory() {} 
    void UpdateItemQtyInInventory() {} 
    void RemoveItemFromInventory() {} 

private: 
    vector<Item*> inventory; 
}; 

请给我一个提示。我觉得解决方案必须简单，但我已经完全陷入了数天。

感谢您的帮助。

编辑： 我仍然收到一堆错误，并认为我需要多说一点我的代码： 我有一个基类Item和两个派生类Produce和Book。然后，我有四个功能调用：

// Print all items in the inventory 
void PrintInventory(vector<Item*> inventory); 

// Dialogue to create a new item, then add that item to the inventory 
vector<Item*> AddItemToInventory(vector<Item*> inventory); 

// Dialogue to update the quantity of an item, then update that item in the inventory 
vector<Item*> UpdateItemQtyInInventory(vector<Item*> inventory); 

// Dialogue to remove a specific item, then remove that specific item from the inventory 
vector<Item*> RemoveItemFromInventory(vector<Item*> inventory); 

接下来是，现在有没有回报4个转换功能和无参数原本未类库存里面，面前放参数/返回主，我班库存。

这里是整个代码，我认为这是更好地理解是这样的：

#include <iostream> 
#include <string> 
#include <vector> 
#include <sstream> 
#include <cstring> 
using namespace std; 

class Item { 
public: 
    void SetName(string nm) 
    { 
     name = nm; 
    }; 
    void SetQuantity(int qnty) 
    { 
     quantity = qnty; 
    }; 
    void SetPrice(int prcInDllrs) //step1 
    { 
     priceInDollars = prcInDllrs; //step1 
    }; 
    virtual void Print() 
    { 
     cout << name << " " << quantity << endl; 
    }; 
    virtual ~Item() 
    { 
     return; 
    }; 
protected: 
    string name; 
    int quantity; 
    int priceInDollars; //step1 
}; 

class Produce : public Item { // Derived from Item class 
public: 
    void SetExpiration(string expir) 
    { 
     expiration = expir; 
    }; 
    void Print() 
    { 
     cout << name << " x" << quantity 
      << " for $" << priceInDollars //step1 
      << " (Expires: " << expiration << ")" 
      << endl; 
    }; 
private: 
    string expiration; 
}; 

//step 2 add derived class Book 
class Book : public Item { // Derived from Item class 
public: 
    void SetAuthor(string authr) //create author function with parameter 
    { 
     author = authr; 
    }; 
    void Print() 
    { 
     cout << name << " x" << quantity 
      << " for $" << priceInDollars //step1 
      << " (Author: " << author << ")" 
      << endl; 
    }; 
private: 
    string author; 
}; 

// Print all items in the inventory 
void PrintInventory(vector<Item*> inventory); 

// Dialogue to create a new item, then add that item to the inventory 
vector<Item*> AddItemToInventory(vector<Item*> inventory); 

// Dialogue to update the quantity of an item, then update that item in the inventory 
vector<Item*> UpdateItemQtyInInventory(vector<Item*> inventory); 

// Dialogue to remove a specific item, then remove that specific item from the inventory 
vector<Item*> RemoveItemFromInventory(vector<Item*> inventory); 

int main() { 
    vector<Item*> inventory; 
    string usrInptOptn = "default"; 

    while (true) { 
     // Get user choice 
     cout << "\nEnter (p)rint, (a)dd, (u)pdate, (r)emove, or (q)uit: "; 
     getline(cin, usrInptOptn); 

     // Process user choice 
     if (usrInptOptn.size() == 0) { 
      continue; 
     } 
     else if (usrInptOptn.at(0) == 'p') { 
      PrintInventory(inventory); 
     } 
     else if (usrInptOptn.at(0) == 'a') { 
      inventory = AddItemToInventory(inventory); 
     } 
     else if (usrInptOptn.at(0) == 'u') { 
      inventory = UpdateItemQtyInInventory(inventory); 
     } 
     else if (usrInptOptn.at(0) == 'r') { 
      inventory = RemoveItemFromInventory(inventory); 
     } 
     else if (usrInptOptn.at(0) == 'q') { 
      cout << "\nGood bye." << endl; 
      break; 
     } 
    } 

    return 0; 
} 

class Inventory { 
public: 

    void PrintInventory() { 
     unsigned int i = 0; 
     if (inventory.size() == 0) { 
      cout << "No items to print." << endl; 
     } 
     else { 
      for (i = 0; i<inventory.size(); ++i) { 
       cout << i << " - "; 
       inventory.at(i)->Print(); 
      } 
     }; 
    } 
    void AddItemToInventory() { 


     Produce* prdc; 
     Book* book; //create new pointer object of class book 
     string usrInptName = ""; 
     string usrInptQntyStr = ""; 
     istringstream inSS; 
     int usrInptQnty = 0; 
     string usrInptExpr = ""; 
     int usrInptPrc = 0; //step1 
     string usrInptAuthr = ""; //declare variable 
     string usrInptBookName = ""; 
     int usrInptQntyBook = 0; 
     string usrInptQntyBookStr = ""; 
     string usrInptChoice = " "; 


     //loop user choice and ask again if choice is not valid 
     do { 
      cout << "Enter choice of adding (b)ook or (p)roduce: "; 
      getline(cin, usrInptChoice); 
      if (usrInptChoice != "b" && usrInptChoice != "p") { 
       cout << "Invalid Choice" << endl; 
      } 
     } while (usrInptChoice != "b" && usrInptChoice != "p"); 

     //only ask for inventory type accoring to user input p or b 
     if (usrInptChoice == "p") { 

      cout << "Enter name of new produce: "; 
      getline(cin, usrInptName); 

      cout << "Enter quantity: "; 
      getline(cin, usrInptQntyStr); 
      inSS.str(usrInptQntyStr); 
      inSS >> usrInptQnty; 
      inSS.clear(); 

      cout << "Enter expiration date: "; 
      getline(cin, usrInptExpr); 

      cout << "Enter the price per item : $"; //step1 
      cin >> usrInptPrc; //step1 

      prdc = new Produce; 
      prdc->SetName(usrInptName); 
      prdc->SetQuantity(usrInptQnty); 
      prdc->SetExpiration(usrInptExpr); 
      prdc->SetPrice(usrInptPrc); 

      inventory.push_back(prdc); 
     } 

     if (usrInptChoice == "b") { 
      cout << "Enter name of new book: "; 
      getline(cin, usrInptBookName); 

      cout << "Enter quantity: "; 
      getline(cin, usrInptQntyBookStr); 
      inSS.str(usrInptQntyBookStr); 
      inSS >> usrInptQntyBook; 
      inSS.clear(); 

      cout << "Enter author: "; 
      getline(cin, usrInptAuthr); 

      cout << "Enter the price per item : $"; //step1 
      cin >> usrInptPrc; //step1 

      book = new Book; 
      book->SetName(usrInptBookName); 
      book->SetQuantity(usrInptQntyBook); 
      book->SetAuthor(usrInptAuthr); 
      book->SetPrice(usrInptPrc); 

      inventory.push_back(book); 
     }; 
    } 

    void UpdateItemQtyInInventory() { 
     string usrIndexChoiceStr = ""; 
     unsigned int usrIndexChoice = 0; 
     istringstream inSS; 
     string usrInptQntyStr = ""; 
     int usrInptQnty = 0; 

     if (inventory.size() == 0) { 
      cout << "No items to update." << endl; 
     } 
     else { 
      PrintInventory(); 

      do { 
       cout << "Update which item #: "; 
       getline(cin, usrIndexChoiceStr); 
       inSS.str(usrIndexChoiceStr); 
       inSS >> usrIndexChoice; 
       inSS.clear(); 
      } while (!(usrIndexChoice < inventory.size())); 

      cout << "Enter new quantity: "; 
      getline(cin, usrInptQntyStr); 
      inSS.str(usrInptQntyStr); 
      inSS >> usrInptQnty; 
      inSS.clear(); 

      inventory.at(usrIndexChoice)->SetQuantity(usrInptQnty); 
     }; 
    } 

    void RemoveItemFromInventory() { 
     istringstream inSS; 
     string usrIndexChoiceStr = ""; 
     unsigned int usrIndexChoice = 0; 
     string usrInptQntyStr = ""; 

     if (inventory.size() == 0) { 
      cout << "No items to remove." << endl; 
     } 
     else { 
      PrintInventory(); 

      do { 
       cout << "Remove which item #: "; 
       getline(cin, usrIndexChoiceStr); 
       inSS.str(usrIndexChoiceStr); 
       inSS >> usrIndexChoice; 
       inSS.clear(); 
      } while (!(usrIndexChoice < inventory.size())); 

      inventory.erase(inventory.begin() + usrIndexChoice); 
     }; 
    } 

    private: 
     vector<Item*> inventory; 
}; 

我没有在Visual Studio中得到任何编译错误，但是当我尝试建立，有5个错误。编译在Geany程序没有给我任何的错误，但是当我建立了，它说：

undefined reference to `PrintInventory(std::vector<Item*, std::allocator<Item*> >)' 
    undefined reference to `AddItemToInventory(std::vector<Item*, std::allocator<Item*> >)' 
    undefined reference to `UpdateItemQtyInInventory(std::vector<Item*, std::allocator<Item*> >)' 
    undefined reference to `RemoveItemFromInventory(std::vector<Item*, std::allocator<Item*> >)' 
    collect2.exe: error: ld returned 1 exit status 
    Compilation failed. 

我觉得我缺少一些基本的，简单的事情，但我无法弄清楚。当我说要将函数PrintInventory，AddItemToInventory，UpdateItemQtyInInventory， 和RemoveItemFromInventory转换为void/no参数，但是它涉及到哪些函数时，该指令让我感到困惑。四条定义线？实际功能？都？那么主要和其他课程呢？我不需要改变那里的事吗？

Answer 1

基本测试：

注意，也有在这里

void test() 
{ 
    class T_item 
    { 
    public: 
     string name; 
     int quantity; 
     int priceInDollars; 
    }; 

    vector<T_item> inventory; 

    T_item temp; 

    //add item: 
    temp.name = "name1"; 
    temp.quantity = 1; 
    temp.priceInDollars = 1; 
    inventory.push_back(temp); 

    temp.name = "name2"; 
    temp.quantity = 2; 
    temp.priceInDollars = 2; 
    inventory.push_back(temp); 

    cout << "print:\n"; 
    for each(T_item item in inventory) 
    { 
     cout << item.name << endl; 
     cout << item.quantity << endl; 
     cout << item.priceInDollars << endl << endl; 
    } 

    //modify item at index 1: 
    inventory[1].name = "modified"; 

    //delete item at index 0: 
    inventory.erase(inventory.begin() + 0); 

    cout << "print again:\n"; 
    for each(T_item item in inventory) 
    { 
     cout << item.name << endl; 
     cout << item.quantity << endl; 
     cout << item.priceInDollars << endl << endl; 
    } 
} 

int main() 
{ 
    test(); 
    return 0; 
} 

Answer 2

没有指针，我相信你的代码的转换是否正确。由于“库存向量”是一个成员变量，因此它可以被所有其他成员函数访问，也可以被操纵。这消除了将向量作为参数传递的要求。 现在为了返回矢量，我建议添加一个新的“GetInventory（）”方法，该方法返回矢量或采用引用来传递矢量。

希望它有帮助。

Answer 3

感谢WhozCraig，我的问题已经解决：

“库存的类定义必须来之前的主（）以某种方式将它上面的main（），它应该工作。”