C++ function的重新定义

Question

I have a base class and 3 separate derived classes. All of the.hpp files are structured the same.

The.hpp which doesn't work:

#ifndef CAESARCIPHER_HPP
#define CAESARCIPHER_HPP
#include "Cipher.hpp"
#include<string>

class CaesarCipher : public Cipher {
    public:
        CaesarCipher(Key key)
            : Cipher{ key } {}
        
        std::string getCipherTypeString() const override {}
};
#endif

The.cpp of it (haven't implemented anything yet):

  #include "CaesarCipher.hpp"
    #include "Cipher.hpp"
    #include<iostream>
    
    CaesarCipher::CaesarCipher(Key key)
        : Cipher{ key } {}
    
    std::string CaesarCipher::getCipherTypeString() const {
        return "";
    }

One.hpp that does work:

 #ifndef ASCIICIPHER_HPP
    #define ASCIICIPHER_HPP
    #include "Cipher.hpp"
    #include<string>
    
    class AsciiCipher : public Cipher {
        public:
            AsciiCipher(Key key)
                : Cipher{ key } {}
           
            std::string getCipherTypeString() const override {}
         
};
    #endif

The base.hpp class looks like this:

typedef uint64_t Key;


    #ifndef BASE_HPP
    #define BASE_HPP
    #include <string>    

class Cipher {
    Key key_;
    public: 
        Cipher(Key key){}
        
        virtual std::string getCipherTypeString() const {}
       
        
};
    #endif

Errors:

CaesarCipher.cpp:6:15: error: redefinition of 'CaesarCipher'
CaesarCipher::CaesarCipher(Key key)
              ^
./CaesarCipher.hpp:9:9: note: previous definition is here
        CaesarCipher(Key key)
        ^
CaesarCipher.cpp:9:27: error: redefinition of 'getCipherTypeString'
std::string CaesarCipher::getCipherTypeString() const {
                          ^
./CaesarCipher.hpp:12:21: note: previous definition is here
        std::string getCipherTypeString() const override {}
                    ^

The problem is that 2 of the derived classes work perfectly but for one I get the above mentioned error for all of the functions. They look all the same just with changed names etc.

Answer 1

You have to:

• Define the type Key .
• Provide the missing body for the definition of Base::Base(Key) .
• Add a return statement to all functions that return non-void.

That should fix the errors that you are getting.