Question

错误说明：
“错误：虚拟外部类定义”

有问题的Cpp成员：

virtual void Account::creditBalance(double plus)
{
   if(plus > 0)
      balance += plus;
   else
      cout << "Cannot credit negative.";
}

virtual void Account::debitBalance(double minus)
{
   if(minus <= balance)
      balance -= minus;
   else
      cout << "Debit amount exceeded account balance.";
}

其余代码在这里（虽然我不确定是否有必要）：http://pastebin.com/de5e9f77

Answer 1

简单地剥离方法定义的虚拟。仅在声明时才需要virtual关键字。

示例：

class Account {
public:
  virtual void creditBalance(double);
  virtual void debitBalance(double);
};

void Account::creditBalance(double plus)
{
   if(plus > 0)
      balance += plus;
   else
      cout << "Cannot credit negative.";
}

void Account::debitBalance(double minus)
{
   if(minus <= balance)
      balance -= minus;
   else
      cout << "Debit amount exceeded account balance.";
}

Answer 2

您只需要在类声明中使用virtual关键字，即在头文件中。因此，将您的cpp文件更改为：

void Account::creditBalance(double plus)
{
   if(plus > 0)
      balance += plus;
   else
      cout << "Cannot credit negative.";
}

void Account::debitBalance(double minus)
{
   if(minus <= balance)
      balance -= minus;
   else
      cout << "Debit amount exceeded account balance.";
}

Answer 3

仅在声明中使用virtual关键字（在头文件中，在类定义中）而不是在实现中（通常是.cc文件）

使C ++函数虚拟时出错

3 个答案: