C++模板嵌套类

12.14 C++模板嵌套类

在模板类中中嵌套类：模板类为QueueTP，嵌套类为Node

代码：

queuetp.h

#pragma once
// 这是队列---先入先出的思想
#ifndef QUEUETP_H_
#define QUEUETP_H_
template 
class QueueTP
{
private:
    enum { Q_SIZE = 10 };
    // Node is a nested class definition
    class Node
    {
    public:
        Item item;
        Node* next;
        Node(const Item& i) :item(i), next(0) { }
    };
    Node* front; // pointer to front of Queue
    Node* rear; // pointer to rear of Queue
    int items; // current number of items in Queue
    const int qsize; // maximum number of items in Queue
    QueueTP(const QueueTP& q) : qsize(0) {}  //复制构造函数
    QueueTP& operator=(const QueueTP& q) { return *this; }  //赋值运算符重载
public:
    QueueTP(int qs = Q_SIZE);//默认构造函数
    ~QueueTP();//析构函数
    bool isempty() const
    {
        return items == 0;
    }
    bool isfull() const
    {
        return items == qsize;
    }
    int queuecount() const
    {
        return items;
    }
    bool enqueue(const Item& item); // add item to end
    bool dequeue(Item& item); // remove item from front
};
// QueueTP methods
template 
QueueTP::QueueTP(int qs) : qsize(qs)
{
    front = rear = 0;
    items = 0;
}
template 
QueueTP::~QueueTP()
{
    Node* temp;
    while (front != 0) // while queue is not yet empty
    {
        temp = front; // save address of front item
        front = front->next;// reset pointer to next item
        delete temp; // delete former front
    }
}
// Add item to queue
template 
bool QueueTP::enqueue(const Item& item)
{
    if (isfull())
        return false;
    Node* add = new Node(item); // create node
    // on failure, new throws std::bad_alloc exception
    items++;
    if (front == 0) // if queue is empty,
        front = add; // place item at front
    else
        rear->next = add; // else place at rear
    rear = add; // have rear point to new node
    return true;
}
// Place front item into item variable and remove from queue
template 
bool QueueTP::dequeue(Item& item)
{
    if (front == 0)
        return false;
    item = front->item; // set item to first item in queue
    items--;
    Node* temp = front; // save location of first item
    front = front->next; // reset front to next item
    delete temp; // delete former first item
    if (items == 0)
        rear = 0;
    return true;
}
#endif

main.cpp

/*
Project name :          _16Nested_class
Last modified Date:     2022年3月28日09点39分
Last Version:           V1.0
Descriptions:           嵌套类
*/
#include
#include"queuetp.h"
#include"queue.h"
#include
​
int main()
{
    using std::string;
    using std::cin;
    using std::cout;
    /*
    模板类中的嵌套类
    相关的文件：queuetp.h
    */
    QueueTP cs(2);
    while (!cs.isfull())
    {
        cout << "Please enter your name. You will be "
            "served in the order of arrival.\n"
            "name: ";
        getline(cin, temp);
        cs.enqueue(temp);
    }
    cout << "The queue is full. Processing begins!\n";
    while (!cs.isempty())
    {
        cs.dequeue(temp);
        cout << "Now processing " << temp << "...\n";
    }
    return 0;
}

运行结果：

Please enter your name. You will be served in the order of arrival.
name: Jasmine
Please enter your name. You will be served in the order of arrival.
name: lili
The queue is full. Processing begins!
Now processing Jasmine...
Now processing lili...
​
D:\Prj\_C++Self\_16Nested_class\Debug\_16Nested_class.exe (进程 15116)已退出，代码为 0。
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