爲什麼我得到對Class :: Class（）的undefined引用？

Question

錯誤：未定義參考`事務::交易（QString的，QDATE，整型，雙）」

從頭文件提取物：

#include <Transaction.h> 

class Product 
{ 
public: 
    virtual ~Product(); 
    void sell(int n); 
    void restock(int n); 
    void setProductCode(QString c); 

    QString getSupplierCode() const; 
    QString getProductCode() const; 
    QList<Transaction> getTransactions(); 

    QString toString(); 
    void removeAll(); 
    bool isExpired() const; 

protected: 
    Product(QString name, int num, double seprice, double suprice, QString sc); 
    Product(QStringList& prodlist); 

private: 
    QString m_Name; 
    int m_NoOfItems; 
    QString m_ProductCode; 
    double m_SellingPrice; 
    double m_SupplierPrice; 
    QString m_SupplierCode; 
    QList<Transaction> m_Transaction; 
}; 

執行文件：

//Sell a product 
void Product::sell(int n) 
{ 
    if(m_NoOfItems == 0) 
    { 
    qDebug() << "Out of stock"; 
    } 
    else if(n < m_NoOfItems) 
    { 
     m_NoOfItems = m_NoOfItems -n; 
     m_Transaction.append(Transaction("Sale", QDate::currentDate(),n, m_SellingPrice)); 
    } 
    else qDebug() << "Not enough items in stock"; 
} 

//Restock a product 
void Product::restock(int n) 
{ 
    m_NoOfItems = m_NoOfItems +n; 
    m_Transaction.append(Transaction("Purchase", QDate::currentDate(),n, `m_SupplierPrice));` 
} 

---

Transaction.h

#ifndef TRANSACTION_H 
#define TRANSACTION_H 

#include <QString> 
#include <QDate> 

//begining of Transaction Class 
class Transaction 
{ 
public: 
    Transaction(QString type, QDate date, int num, double price); 
    QString toString() const; 

private: 
    QString m_Type; 
    QDate m_Date; 
    int m_NoOfItems; 
    double m_PricePerItem; 

}; 
//end of Transaction class 
#endif // TRANSACTION_H 

我得到未定義的參考Transaction::Transaction(QString, QDate, int, double)。它應該和上面一樣。我已經提到了class :: class，因爲我已經提到過這個類。

Answer 1

交易類不可見。我已經在同一個文件的Product類下面定義了它。我不得不把它放在一個單獨的頭文件中。