为什么我得到对 Class::Class() 的未定义引用？

Question

错误：未定义对`Transaction::Transaction(QString, QDate, int, double)'的引用

从头文件中提取：

#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;
};

执行文件：

//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

我得到了对 Transaction::Transaction(QString, QDate, int, double) 的未定义引用。应该是如上。我已经把 class::class 作为我已经提到的 class 问题。

Answer 1

交易 class 不可见。我在同一个文件中的 Product class 下面定义了它。我不得不把它放在一个单独的头文件中。

为什么我得到对 Class::Class() 的未定义引用？

Why am I getting undefined reference to Class::Class()?

c++

undefined-reference