c++ - 调试继承类

Question

我在运行代码时收到以下错误，似乎我已经尝试了一切方法来消除它们，但似乎没有任何效果。 任何有关我可能做错的事情的建议或解释将不胜感激。以下是错误: 在我的代码“class Integer:public Number”中，它说“!预期的类名” 和“Integer(const Double &d);”它说“!未知类型名称'Double'；您的意思是'double'吗？”

这里是Integer.h中可能包含错误的实际代码:

#ifndef INTEGER
#define INTEGER

#include "Number.h"
#include "Double.h"

namespace MyNamespace {

using std::string;

class Double;

class Integer : public Number

{

private:

    void create(int i);

    bool NaN(string s, int iCount);

    bool nan;

public:

    //Constructors

    Integer();

    Integer(int i);

    Integer(const Integer &i);

    Integer(const Double &d);  //ERROR HERE = "Unknown type 'Double'"

    Integer(string s);


    void equals(int i);

    void equals(string s);

    Integer add(const Integer &i);

    Integer sub(const Integer &i);

    Integer mul(const Integer &i);

    Integer div(const Integer &i);

    Integer add(int i);

    Integer sub(int i);

    Integer mul(int i);

    Integer div(int i);

    int toInt() const;


    //Print
    void printInteger();


    // operator overloads

    Integer operator + (const Integer &i);

    Integer operator - (const Integer &i);

    Integer operator * (const Integer &i);

    Integer operator / (const Integer &i);

    Integer operator = (const Integer &i);

    Integer operator = (int i);

    Integer operator = (string s);

    string toString() const;

    bool operator == (const Integer &i);

    bool operator == (int i);

    bool operator != (const Integer &i);

    bool operator != (int i);


    bool isNan();

};
}

#endif

Number.h

#ifndef NUMBER
#define NUMBER

#include <iostream>
#include <string>

namespace MyNamespace {

using std::string;

class Number : public string
{

public:

    Number();

    Number(string s);


};

}

#endif

双.h

#ifndef DOUBLE
#define DOUBLE

#include "Number.h"
#include "Integer.h"

namespace MyNamespace
{

class Integer;    

class Double : public Number

{

private:

    void create(double d);

    bool NaN(string s, int dCount);

    bool nan;

public:

    // Constructors

    Double();

    Double(double d);

    Double(const Double &d);

    Double(const Integer &i);  //ERROR HERE = "Unknown type 'Integer'"

    Double(string s);


    void equals(double d);

    void equals(string s);

    Double add(const Double &d);

    Double sub(const Double &d);

    Double mul(const Double &d);

    Double div(const Double &d);

    Double add(double d);

    Double sub(double d);

    Double mul(double d);

    Double div(double d);

    double toDouble() const;

    //Print
    void printDouble();

    // operator overloads

    Double operator + (const Double &d);

    Double operator - (const Double &d);

    Double operator * (const Double &d);

    Double operator / (const Double &d);

    Double operator = (const Double &d);

    Double operator = (double d);

    Double operator = (string s);

    string toString() const;

    bool operator == (const Double &d);

    bool operator == (double d);

    bool operator != (const Double &d);

    bool operator != (double d);


    bool isNan();

};
}

#endif

Answer 1

Integer 和 Double 之间存在循环依赖关系。如果您不使用这些内联，您可能只有一个前向声明并删除#include“Integer.h”和#include“Double.h”。

如果您想使用这些内联，您可能会包含用于内联实现的其他文件:

#ifndef NUMBER_H
#define NUMBER_H

#include <iostream>
#include <string>


namespace MyNamespace {

// Please do not put the using into the global namespace
using std::string;

class Number : public string {};

}
#endif

// =============================================================================

#ifndef INTEGER_H
#define INTEGER_H

#include "Number.h"

namespace MyNamespace {

class Double;
class Integer : public Number
{
public:
    Integer(const Double &d);
};
}

#endif

#include "Integer.tcc"

// =============================================================================

// Integer.tcc
#ifndef INTEGER_H
#error Please include Integer.h instead
#endif

#include "Double.h"

namespace MyNamespace {
    inline Integer::Integer(const Double &d) {}
}

// =============================================================================

#ifndef DOUBLE_H
#define DOUBLE_H

#include "Number.h"

namespace MyNamespace
{

class Integer;
class Double : public Number
{
public:
    Double(const Integer &i);
};
}

#endif

#include "Double.tcc"

// =============================================================================

// Double.tcc
#ifndef DOUBLE_H
#error Please include Double.h instead
#endif

#include "Integer.h"

namespace MyNamespace {
    inline Double::Double(const Integer &d) {}
}