error: passing const std::string as this argument

This is a discussion on error: passing const std::string as this argument within the C++ Programming forums, part of the General Programming Boards category; The Following is my Code FileNotReadableException Signature Code: class FileNotReadableException : public CGIException{ protected: const string& fileName; public: FileNotReadableException(); FileNotReadableException(const ...

  1. #1
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    Jun 2007
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    219

    error: passing const std::string as this argument

    The Following is my Code

    FileNotReadableException Signature
    Code:
    class FileNotReadableException : public CGIException{
    	protected:
    		const string& fileName;
    	public:
    		FileNotReadableException();
    		FileNotReadableException(const string& file);
    		~FileNotReadableException();
    		void setFileName(const string& file);
    		const string& getFileName() const;
    };
    FileNotReadableException Implementation
    Code:
    FileNotReadableException::FileNotReadableException():fileName(""), CGIException(){
    
    }
    
    FileNotReadableException::FileNotReadableException(const string& file):fileName(file), CGIException("CGI::System::FileUnReadable", ("File: "+fileName+" Couldn't be opened for reading")){
    
    }
    
    void FileNotReadableException::setFileName(const string& file){
    	fileName = file;//Line 43 Here is teh Error
    }
    
    const string& FileNotReadableException::getFileName() const{
    	return fileName;
    }
    
    FileNotReadableException::~FileNotReadableException(){
    
    }
    It yields the following Compiler Error.
    Code:
    Line 43: error: passing ‘const std::string’ as ‘this’ argument of ‘std::basic_string<_CharT, _Traits, _Alloc>& std::basic_string<_CharT, _Traits, _Alloc>::operator=(const std::bas.........

  2. #2
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    Jun 2007
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    219
    solved by using string instead of const string&
    I can understand why the const was making the problem (const-correctness)
    But cant understand why the reference was making a Problem cause I am initializing all of them on teh Constructor.

  3. #3
    Registered User
    Join Date
    Jan 2005
    Posts
    7,317
    Your member variable shouldn't be const if you are modifying it. It can be a reference, that wasn't causing that problem. But it shouldn't be because you want the string to be owned by the object, not refer to some other string from outside. Making filename a string is the correct choice.

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