Question

我是C ++新手。我在另一个类中继承了一个类，但是我收到一条错误消息：

error: no matching function for call to ‘Extended_queue::append(const Plane&)’

我做错了什么？我的部分代码如下：

#include<iostream>
using namespace std;
#include "runway.h"

Runway::Runway(int limit)
/*
 Post:  The Runway data members are initialized to record no
 prior Runway use and to record the limit on queue sizes.
 */

{
    queue_limit = limit;
    num_land_requests = num_takeoff_requests = 0;
    num_landings = num_takeoffs = 0;
    num_land_refused = num_takeoff_refused = 0;
    num_land_accepted = num_takeoff_accepted = 0;
    land_wait = takeoff_wait = idle_time = 0;
}

Error_code Runway::can_land(const Plane &current)
/*
 Post:  If possible, the Plane current is added to the
 landing Queue; otherwise, an Error_code of overflow is
 returned. The Runway statistics are updated.
 Uses:  class Extended_queue.
 */

{
    Error_code result;
    if (landing.size() < queue_limit)
        result = landing.append(current);
    else
        result = fail;
    num_land_requests++;

    if (result != success)
        num_land_refused++;
    else
        num_land_accepted++;

    return result;
}

错误在result = landing.append(current);行头部queue.h在runway.h中引用。我在下面列出了queue.h

const int maxqueue = 10; // small value for testing

struct Queue_entry {
    struct Queue_entry *next;
    struct Queue_entry *prev;
};

typedef struct Queue_entry    *queue_t;
typedef struct Queue_entry    queue_head_t;
typedef struct Queue_entry    queue_chain_t;
typedef struct Queue_entry    *queue_entry_t;

class Queue {
public:
    Queue();
    bool empty() const;
    Error_code serve();
    Error_code append(const Queue_entry &item);
    Error_code retrieve(Queue_entry &item) const;
protected:
    int count;
    int front, rear;
    Queue_entry entry[maxqueue];
};

class Extended_queue: public Queue {
public:
    bool full() const;
    int size() const;
    void clear();
    Error_code serve_and_retrieve(Queue_entry &item);
};

runway.h的代码如下所示

#include "plane.h"
#include "queue.h"

enum Runway_activity {idle, land, takeoff};

class Runway {

public:
    Runway(int limit);
    Error_code can_land(const Plane &current);
    Error_code can_depart(const Plane &current);
    Runway_activity activity(int time, Plane &moving);
    void shut_down(int time) const;

private:
    Extended_queue landing;
    Extended_queue takeoff;
    int queue_limit;
    int num_land_requests; //  number of planes asking to land
    int num_takeoff_requests; //  number of planes asking to take off
    int num_landings; //  number of planes that have landed
    int num_takeoffs; //  number of planes that have taken off
    int num_land_accepted; //  number of planes queued to land
    int num_takeoff_accepted; //  number of planes queued to take off
    int num_land_refused; //  number of landing planes refused
    int num_takeoff_refused; //  number of departing planes refused
    int land_wait; //  total time of planes waiting to land
    int takeoff_wait; //  total time of planes waiting to take off
    int idle_time; //  total time runway is idle
};

Runway.h引用plane.h，其中包括：

enum Plane_status {
    null, arriving, departing
};

class Plane {
public:
    Plane();
    Plane(int flt, int time, Plane_status status);
    void refuse() const;
    void land(int time) const;
    void fly(int time) const;
    int started() const;

private:
    int flt_num;
    int clock_start;
    Plane_status state;
};

为什么编译器无法识别Queue中Extended_queue继承的方法？

Answer 1

您的错误是您正在将Plane对象传递给

Extended_queue :: append（const Queue_entry＆amp; item）

其中 Extended_queue 是父类队列的子类。

您尚未定义可以使用Plane对象的Queue :: append版本。
或者，您尚未指定班级 Plane 为 Queue_entry 类的孩子。

无论哪种方式，您都为函数提供了错误的参数类型。这就像将 int 传递给正在调用 Plane 的函数。

＆＃34;没有用于呼叫＆＃34;的匹配功能在C ++中使用继承对象时出错

1 个答案: