条款12：复制对象时勿忘其每一个成分

当我们编写一个copying函数，请确保（1）复制所有local成员变量，（2）调用所有base class内的适当的copying函数
下面我们来看一个例子怎样来具体实现子类的copying函数
void logCall(const string &funcNmae)
{
 cout << funcNmae << endl;
}

class Customer
{
public:
 Customer(const string &strname) : name(strname)
 {

 }
 Customer(const Customer &rhs);
 Customer& operator=(const Customer &rhs);
private:
 string name;
};

Customer::Customer(const Customer &rhs) : name(rhs.name)
{
 logCall("Customer copy constructor");
}

Customer& Customer::operator=(const Customer &rhs)
{
 logCall("Customer copy assignment operator");
 name = rhs.name;
 return *this;
}

class PriorityCustomer : public Customer
{
public:
 PriorityCustomer( int value, string strname ) : Customer(strname) , priority(value)
 {

 }
 PriorityCustomer(const PriorityCustomer &rhs);
 PriorityCustomer& operator=(const PriorityCustomer &rhs);
private:
 int priority;
};

PriorityCustomer::PriorityCustomer(const PriorityCustomer &rhs)
: Customer(rhs) , priority(rhs.priority)//调用base class的copy构造函数对base class 成员变量进行赋值
{
 logCall("priorityCustomer copy constructor");
}

PriorityCustomer& PriorityCustomer::operator=(const PriorityCustomer &rhs)
{
 logCall("PriorityCustomer copy assignment operator");
 Customer::operator=(rhs); //对base class成分进行赋值动作
 priority = rhs.priority;
 return *this;
}