c++ - 继承问题 : Using header files and default constructor of the base class in the derived class

Question

我有一个简单的问题:这是基类:

class CBox
{
public:

    double m_Length;
    double m_Width;
    double m_Height;
    CBox()
    {

    }
    CBox(double lv=1.0,double wv=1.0,double hv=1.0)
            :m_Length(lv),m_Width(wv),m_Height(hv)
        {
        }
    ~CBox();
protected:
private:
};

这是派生类:

 #ifndef CCANDYBOX_H

    #define CCANDYBOX_H

   #include "CBox.h"

   #include <iostream>

   #include <cstring>


class CCandyBox :CBox
{
    public:
         char* m_Contents;
        CCandyBox(double lv, double mv, double hv, char* str):CBox(lv,mv,hv)
        {
            m_Contents = new char[ strlen(str) +1 ];

            for(unsigned int i=0; i< strlen(str)+1; i++)
            {               *(m_Contents+i) = *(str +i);
            {
                *(m_Contents+i) = *(str+i);
            }

        }
        CCandyBox(char* str = "Candy"):CBox()
        {
              m_Contents = new char[ strlen(str) +1];

              for(unsigned int i=0; i<strlen(str)+1;++i)
              {
                  *(m_Contents +i) = *(str+i);
              }
        }
        virtual ~CCandyBox()
        {
            delete[] m_Contents;
        }
        CCandyBox(const CCandyBox& other);
        CCandyBox& operator=(const CCandyBox& other);
    protected:
    private:
};


#endif // CCANDYBOX_H

Main.cpp 函数只包含“CCandyBox.h”和一个简单的“helloworld”

并给出以下错误:

        C:\Work\Check\main.cpp|4|error: expected nested-name-specifier before 'namespace'|
C:\Work\Check\main.cpp|4|error: expected unqualified-id before 'namespace'|
C:\Work\Check\main.cpp|4|error: expected ';' before 'namespace'|
C:\Work\Check\main.cpp|4|error: expected unqualified-id before 'namespace'|
C:\Work\Check\main.cpp|11|error: expected '}' at end of input|
C:\Work\Check\CCandyBox.h||In constructor 'CCandyBox::CCandyBox(double, double, double, char*)':|
C:\Work\Check\CCandyBox.h|24|error: expected primary-expression before '(' token|
C:\Work\Check\CCandyBox.h|24|error: expected primary-expression before 'char'|
C:\Work\Check\CCandyBox.h|24|error: expected ';' before ':' token|
C:\Work\Check\CCandyBox.h|41|error: expected '}' at end of input|
C:\Work\Check\main.cpp||In member function 'int CCandyBox::main()':|
C:\Work\Check\main.cpp|9|error: 'cout' was not declared in this scope|
C:\Work\Check\main.cpp|9|note: suggested alternative:|
c:\mingw\bin\..\lib\gcc\mingw32\4.6.1\include\c++\iostream|62|note:   'std::cout'|
C:\Work\Check\main.cpp|9|error: 'endl' was not declared in this scope|
C:\Work\Check\main.cpp|9|note: suggested alternative:|
c:\mingw\bin\..\lib\gcc\mingw32\4.6.1\include\c++\ostream|543|note:   'std::endl'|
C:\Work\Check\main.cpp|11|error: expected unqualified-id at end of input|
||=== Build finished: 16 errors, 0 warnings ===|

我正在使用 MinGW 和 CodeBlocks。帮助表示赞赏

Answer 1

1. 对于初学者，我强烈建议让自己的生活变得轻松，并将所有实现主体移动到单独的文件(例如，移动到 CBox.cpp 和 CCandyBox.cpp)。

2. 这是错误的:

   for(unsigned int i=0; i< strlen(str)+1; i++) { *(m_Contents+i) = *(str +i); { *(m_Contents+i) = *(str+i);

3. 这样更好:

   for(unsigned int i=0; i < strlen(str); i++) m_Contents[i] = str[i]; m_Contents[strlen(str)] = '\0';

4. 这更好:

文件 CCandyBox.h:

#ifndef CCANDYBOX_H
#define CCANDYBOX_H

#include <string>
#include "CBox.h"

class CCandyBox : public CBox
{
    public:
    std::string m_Contents;
    ...

文件 CCandyBox.cpp:

#include <string.h>
#include "CCandyBox.h"
...
CCandyBox::CCandyBox(double lv, double mv, double hv, char* str)
  : CBox(lv,mv,hv)
{
  m_Contents = std::string(str);
  ...