c++ - 实际声明了“未声明的标识符”

Question

对于我在类头文件中声明为公共数据成员、一个 int 和一个指向该 int 的指针的变量，我一直收到错误 C2065s。仅当我在函数中使用这些变量时才标记为错误的代码行 - 在类的构造函数中，它们似乎可以通过。

我正在使用 Visual Studio 2010 Express 编写普通的 C++（不是 Visual C++），这是编译器错误日志的输出：

1>------ Build started: Project: Project 2, Configuration: Debug Win32 ------
1>  BaseClassWithPointer.cpp
1>d:\libraries\documents\school\advanced c++\project 2\project 2\baseclasswithpointer.cpp(27): error C2065: 'q' : undeclared identifier
1>d:\libraries\documents\school\advanced c++\project 2\project 2\baseclasswithpointer.cpp(27): error C2541: 'delete' : cannot delete objects that are not pointers
1>d:\libraries\documents\school\advanced c++\project 2\project 2\baseclasswithpointer.cpp(32): error C2065: 'num' : undeclared identifier
1>d:\libraries\documents\school\advanced c++\project 2\project 2\baseclasswithpointer.cpp(33): error C2065: 'q' : undeclared identifier
1>d:\libraries\documents\school\advanced c++\project 2\project 2\baseclasswithpointer.cpp(34): error C2065: 'q' : undeclared identifier
1>  Generating Code...
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

最后，这是我的代码块和标题：

BaseClassWithPointer.h

#pragma once
#include <iostream>

using namespace std;

class BaseClassWithPointer
{
public:
    int num;
    int *q;
    BaseClassWithPointer();
    BaseClassWithPointer(int value);
    BaseClassWithPointer(const BaseClassWithPointer& otherObject);
    void destroyPointer();
    virtual void print();
    virtual ~BaseClassWithPointer();                                                        //Destructor is virtual so that derived classes use their own version of the destructor. ~     (2. Inheritance - base class with pointer variables – destructors.)
    const BaseClassWithPointer& operator= (const BaseClassWithPointer &rhs);        //Assignment operator is overloaded to avoid shallow copies of pointers. ~ (3. Inheritance     – base class with pointer variables – assignment operator overloading.)

};

BaseClassWithPointer.cpp

#pragma once
#include "BaseClassWithPointer.h"
#include <iostream>

using namespace std;

BaseClassWithPointer::BaseClassWithPointer()
{
    num = 0;
    q = &num;
}

BaseClassWithPointer::BaseClassWithPointer(int value)
{
    num = value;
    q = &num;
}

BaseClassWithPointer::BaseClassWithPointer(const BaseClassWithPointer& otherObject)
{
    num = otherObject.num;
    q = &num;
}

void destroyPointer()
{
    delete q;
}

void print()
{
    cout << "Num: " << num << endl;
    cout << "Value pointed to by q: " << *q << endl;
    cout << "Address of q: " << q << endl;
}

BaseClassWithPointer::~BaseClassWithPointer()
{
    destroyPointer();
}

const BaseClassWithPointer& BaseClassWithPointer::operator=(const BaseClassWithPointer &rhs)
{
    if (this != &rhs)
    {
        num = rhs.num;
        q = &num;
    }

    return *this;
}

Answer 1

您忘记了 destroyPointer() 方法的类标识符。尝试

void BaseClassWithPointer::destroyPointer()

反而

Answer 2

这个：

void destroyPointer()

...

void print()

应该

void BaseClassWithPointer::destroyPointer()
{
....
}

void BaseClassWithPointer::print()
{
....
}

等等

Answer 3

函数 destroyPointer() 不是 cpp 文件中类的一部分。它应该是：

void BaseClassWithPointer::destroyPointer()
{
  delete q;
}

但是：

void destroyPointer()
{
  delete q;
}

这就是为什么它找不到 q