Appending and reading binary file - c++

Question

I am confused as to where in my code am I getting it wrong. Instead of resulting to 1,2,3 the output is 1,1,1. Any suggestions as to what I can do? I am guessing my error lies either in the writing data or when I use the variable value.
class Binary
{
public:
Binary(int num);
~Binary();
void createBinary();
void writeBinary();
void readBinary();
string binFile;
int value;
fstream binaryFile;
};
Binary::Binary(int num)
{
value = num;
binFile = "BinaryFile.bin";
}
Binary::~Binary()
{
}
void Binary::createBinary()
{
binaryFile.open(binFile, ios::out | ios::binary);
binaryFile.close();
}
void Binary::writeBinary()
{
if (!binaryFile) //if file does not exist
{
createBinary();
}
binaryFile.open(binFile, ios::app | ios::binary);
binaryFile.write((char*)&value, sizeof(value));
binaryFile.close();
}
void Binary::readBinary()
{
binaryFile.open(binFile, ios::in |ios::binary);
binaryFile.read((char*)&value, sizeof(value));
binaryFile.close();
cout << value << ", ";
}
int main()
{
Binary num1(1);
Binary num2(2);
Binary num3(3);
num1.writeBinary();
num2.writeBinary();
num3.writeBinary();
num1.readBinary();
num2.readBinary();
num3.readBinary();
return 0;
}

Answer 1

Since you use a single file and read from start at each Binary()::readBinary(), your result is as expected. Either use different files for each of your objects.
// In general we may need some random part in name but for this special case,
// since you are just writing / reading value, the following seems to work.
Binary::Binary(int num)
{
value = num;
binFile = "BinaryFile"; // common start
binFile += std::to_string(value); // differentiator
binFile += ".bin"; // extension
}
Or, if you want to use the same file, try to get help from a static variable for not to read the same line again and again.