Cant use ofstream as field in c++

Question

I am creating a class for writing file in c++, and i have this code so far,

#include "stdafx.h" #include <iostream> #include <string> #include <stdlib.h> #include <fstream> using namespace std; class FileWriter { private: bool isLittleEndian; ofstream file; public: FileWriter(string fileName) : file("data.bin", ios::out | ios::binary) { int i = 1; char *p = (char *)&i; if(p[0] == 1) isLittleEndian = true; } void writeByte() { } void writeShort() { } void writeInt() { } void writeLong() { } void writeUnsignedByte() { } void writeUnsignedShort() { } void writeUnsignedInt() { } void writeUnsignedLong() { } void writeFloat() { } void writeDouble() { } void writeString() { } void closeFile() { file.close(); } }; int main() { FileWriter writer = FileWriter("C:\\Users\\Owner\\Desktop\\Test.bin"); writer.closeFile(); return 0; }

but for some reason, it wont let me have an ofstream field, and when i try it says, Error 1 error C2248: 'std::basic_ofstream<_Elem,_Traits>::operator =' : cannot access private member declared in class 'std::basic_ofstream<_Elem,_Traits>' c:\users\owner\documents\visual studio 2012\projects\bytetests\bytetests\bytetests.cpp 25 1 I need this because functions in my class need to manipulate this stream. I don't see why this so hard to do.

You shouldn't your code, it makes all the answers irrelevant. But there doesn't seem to be anything obviously wrong now, so the error must be elsewhere. — juanchopanza
– juanchopanza, Commented Oct 17, 2013 at 21:30
@Popgalop I updated my answer which should fix your remaining problem. — Daniel Frey
– Daniel Frey, Commented Oct 17, 2013 at 21:34

juanchopanza · Accepted Answer · 2013-10-17 21:18:06Z

4

You can't copy or assign an std::ofstream, which means you can't do this:

file = openedFile;

You need to either initialize it correctly, or move-copy-assign.

Initialization (preferred option):

FileWriter(string fileName) : file("data.bin", ios::out | ios::binary) { ... }

Move-copy assignment:

file = std::move(openedFile);

Alternatively, you can use the std::ofstream::open method:

file.open("data.bin", ios::out | ios::binary);

edited Oct 17, 2013 at 21:18

answered Oct 17, 2013 at 21:08

juanchopanza

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4 Comments

juanchopanza Over a year ago

@Popgalop I have added some explanation.

Popgalop Over a year ago

i still get this error Error 1 error C2248: 'std::basic_ofstream<_Elem,_Traits>::basic_ofstream' : cannot access private member declared in class 'std::basic_ofstream<_Elem,_Traits>' c:\users\owner\documents\visual studio 2012\projects\bytetests\bytetests\bytetests.cpp 87 1 ByteTests

juanchopanza Over a year ago

@Popgalop I had a typo in my answer, See edit. And simplified example.

Popgalop Over a year ago

i updates my code in my question with your suggested edits but i still get an error

David G · Accepted Answer · 2013-10-17 21:16:46Z

2

file = openedFile;

There is only one operator= defined for basic_ofstream, the move-assignment operator. The copy-assignment operator is implicitly deleted, and so this code will not work.

You need to use the member-initializer list to initialize file with the path:

FileWriter(std::string fileName) : file(fileName, ios::out | ios::binary) { ... }

edited Oct 17, 2013 at 21:16

answered Oct 17, 2013 at 21:09

David G

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4 Comments

Popgalop Over a year ago

I still just get this error 2 IntelliSense: "std::basic_ofstream<_Elem, _Traits>::basic_ofstream(const std::basic_ofstream<_Elem, _Traits>::_Myt &_Right) [with _Elem=char, _Traits=std::char_traits<char>]" (declared at line 1034 of "C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\include\fstream") is inaccessible c:\Users\Owner\Documents\Visual Studio 2012\Projects\ByteTests\ByteTests\ByteTests.cpp 13 11 ByteTests

David G Over a year ago

@Popgalop Remove the original ofstream openFile(...) and file = openedFile

Popgalop Over a year ago

Error 1 error C2248: 'std::basic_ofstream<_Elem,_Traits>::basic_ofstream' : cannot access private member declared in class 'std::basic_ofstream<_Elem,_Traits>' c:\users\owner\documents\visual studio 2012\projects\bytetests\bytetests\bytetests.cpp 84 1 ByteTests

David G Over a year ago

@Popgalop I don't think it has anything to do with the code you just showed us...

Daniel Frey · Accepted Answer · 2013-10-17 21:33:14Z

You can just open the existing object:

file.open("data.bin", ios::out | ios::binary);

And you need to avoid calling (or at least requiring) the copy-ctor of your class. Change

FileWriter writer = FileWriter("C:\\Users\\Owner\\Desktop\\Test.bin");

to:

FileWriter writer("C:\\Users\\Owner\\Desktop\\Test.bin");

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