Thread: Can't access protected data member from base class in derived class

Hi everyone, I have a base class "String" and derived the class "ReverseString" from "String". When I try to use member variables from String in the ReverseString class, it is telling me "ReverseString has no member ' ' "

Here is my ReverseString class:

Code:

class ReverseString : public String{
public:
    ReverseString() : String();
    ReverseString(const ReverseString&) : String(const String&);
    ReverseString(char*) : String(char*);

    friend ReverseString operator+(const ReverseString&, const ReverseString&);
    ReverseString operator~();
};

In the .cpp file for my ReverseString class, it is telling me "ReverseString has no member 'length'"

Code:

...
...
ReverseString operator+(const ReverseString& strA, const ReverseString& strB){
    int len = strA.length + strB.length;
    int count = 0;
    char* temp;
    temp = new char[len];
    for(int i = 0; i < strA.length; i++){
        temp[i] = strA.buf[i];
        count++;
    }
    for(int i = 0; i < strB.length; i++){
        temp[i+count] = strB.buf[i];
    }
    return temp;
}
...
...

Edit: Here is my String class in case you need to see it:

Code:

class String{
protected:
    int length;
    char* buf;
public:
    String();
    String(char*);
    String(char);
    String(int);
    String(const String&);
    String(char, int);
    ~String();

    String& operator=(const String&);
    String& operator=(const char*);
    friend String operator+(const String&, const String&);
    friend String operator+(const String&, const char*);
    friend String operator+(const char*, const String&);
    friend String operator+(const String&, char);
    friend String operator+(char, String&);
    String& operator+=(const String&);
    String operator+() const;
    friend int operator==(const String&, const String&);
    friend int operator!=(const String&, const String&);
    friend int operator<(const String&, const String&);
    friend int operator<=(const String&, const String&);
    friend int operator>(const String&, const String&);
    friend int operator>=(const String&, const String&);
    char& operator[](int);
    friend char* operator+(const String&, int);
    friend char* operator+(int, const String&);
    String& operator++();
    String& operator--();
    String operator++(int);
    String operator--(int);
    friend ostream& operator<<(ostream&, const String&);

    int getLength(const char*);
    String substr(int, int);
    void print();
};

length is a protected member variable in my String class, so shouldn't it be automatically included in the ReverseString class?
(By the way, this isn't the string class from the C++ library)

Thanks in advance!
-Ryan

That problem is not evident from what you have shown, but please do not paraphrase compiler error messages. Always copy and paste the exact error you are getting - ALWAYS!

However, it may be a case of fix the errors starting from the first one reported as each error may cause spurious errors further down.

One very obvious problem I see is this:

Code:

    ReverseString(const ReverseString&) : String(const String&);
    ReverseString(char*) : String(char*);

You wouldn't have made such a silly mistake if you stopped that bad practice of removing parameter names.

It looks like you would also have memory leak issues.

Sorry about that! I always forget to do that when I declare the constructors and functions.

This is my new string class:

Code:

class String{
protected:
    int length;
    char* buf;
public:
    String();
    String(char* str);
    String(char a);
    String(int i);
    String(const String& temp);
    String(char a, int len);
    ~String();

    String& operator=(const String& str);
    String& operator=(const char* a);
    friend String operator+(const String& strA, const String& strB);
    friend String operator+(const String& str, const char* a);
    friend String operator+(const char* a, const String& str);
    friend String operator+(const String& str, char a);
    friend String operator+(char, String& str);
    String& operator+=(const String& str);
    String operator+() const;
    friend int operator==(const String& strA, const String& strB);
    friend int operator!=(const String& strA, const String& strB);
    friend int operator<(const String& strA, const String& strB);
    friend int operator<=(const String& strA, const String& strB);
    friend int operator>(const String& strA, const String& strB);
    friend int operator>=(const String& strA, const String& strB);
    char& operator[](int index);
    friend char* operator+(const String& str, int index);
    friend char* operator+(int index, const String& str);
    String& operator++();
    String& operator--();
    String operator++(int);
    String operator--(int);
    friend ostream& operator<<(ostream& os, const String& str);

    int getLength(const char* a);
    String substr(int a, int b);
    void print();
};

My new Reversestring class:

Code:

class ReverseString : public String {
public:
    ReverseString();
    ReverseString(const ReverseString& strA) : String(strA) {}
    ReverseString(char* a) : String(a) {}

    friend ReverseString& operator+(const ReverseString& strA, const ReverseString& strB);
    ReverseString operator~();
};

And in the .cpp file:

Code:

ReverseString operator+(const ReverseString& strA, const ReverseString& strB){
    int len = strA  .length   + strB. length ; 
    int count = 0;
    ReverseString temp( len );
    for(int i = 0; i < strA. length ; i++){
        temp. buf [i] = strA.buf[i]; 
        count++;
    }
    for(int i = 0; i < strB.length; i++){
        temp.buf[i+count] = strB.buf[i];
    }
    return temp;
}

It's giving me errors on the bold parts ^^
I'm just learning about inheritance...is there something I'm missing (other than the parameter name mistake)?

Thanks

EDIT: I just realized the errors start at the top where I have "#include "string.h"" It says "Error: PCH warning: header stop not at file scope. An intellesense PCH file was not generated."

Ah very good.
Your PCH warning will go away if you put #include "StdAfx.h" as the very first thing in the cpp file, or turn off precompiled headers for that file or the whole project.

As an added exercise, you may want to get familiar with smart pointers.
C9 Lectures: Stephan T. Lavavej - Standard Template Library (STL), 3 of n | C9 Lectures: Stephan T. Lavavej - Standard Template Library (STL) | Channel 9