Compiler returns "synthesized method ‘operator=’ first required here"

Question

I know it may be a simple question, but I've been working on it for the last hour and a half and I'm really lost.

Here the compiler error:

synthesized method ‘File& File::operator=(const File&)’ first required here 

I have this bit of code :

void FileManager::InitManager()
{
    int numberOfFile = Settings::GetSettings()->NumberOfFile() + 1;

    for( unsigned int i = 1; i < numberOfFile; i++ )
    {
        std::string path = "data/data" ;
        path += i;
        path += ".ndb";

        File tempFile( path );

        _files.push_back( tempFile ); // line that cause the error

        /*if( PRINT_LOAD )
        {
            std::cout << "Adding file " << path << std::endl;
        }*/
    }
}

_files if defined in this header :

#pragma once

//C++ Header
#include <vector>

//C Header

//local header
#include "file.h"

class FileManager
{
public:
    static FileManager* GetManager();
    ~FileManager();

    void LoadAllTitle();

private:
    FileManager();
    static FileManager* _fileManager;

    std::vector<File> _files;
};

File is an object I created, it is nothing more than a simple interface to deal with file IO. I have already done vector of user-defined object in the past, but it's the first time I get this error.

Here is the code for the File object: File.h

#pragma once

//C++ Header
#include <fstream>
#include <vector>
#include <string>

//C Header

//local header

class File
{
public:
    File();
    File( std::string path );
    ~File();

    std::string ReadTitle();

    void ReadContent();
    std::vector<std::string> GetContent();

private:
    std::ifstream _input;
    std::ofstream _output;

    char _IO;
    std::string _path;
    std::vector<std::string> _content;
};

File.cpp

#include "file.h"

File::File()
    : _path( "data/default.ndb" )
{
}

File::File( std::string path )
    : _path( path )
{
}

File::~File()
{
}

void File::ReadContent()
{
}

std::string File::ReadTitle()
{
    _input.open( _path.c_str() );
    std::string title = "";

    while( !_input.eof() )
    {
        std::string buffer;
        getline( _input, buffer );

        if( buffer.substr( 0, 5 ) == "title" )
        {
            title = buffer.substr( 6 ); // 5 + 1 = 6... since we want to skip the '=' in the ndb
        }
    }

    _input.close();
    return( title );
}

std::vector<std::string> File::GetContent()
{
    return( _content );
}

I'm working under linux with gcc.

Any hints or tips as to what the solution could be is appreciated.

Sorry for the long post.

Thanks

Answer 1

In C++03, std::vector<T> requires that T be copy-constructable and copy-assignable. File contains standard stream data members, and standard streams are non-copyable, so consequently File is as well.

Your code would work fine in C++11 (with move-construction/move-assignment), but you'll need to avoid holding standard stream objects by value as data members in C++03. I recommend upgrading your compiler to one that supports C++11 move semantics or using one of Boost's smart pointers.

Answer 2

I am not sure about the error message, but this line:

_files.push_back( tempFile );

requires that File have a public copy constructor. Since you have provided other constructors, you also have to provide this one. The compiler doesn't synthesize it.