Convert QString into QByteArray and vice versa.

[freely]

Yes of course it is one of the cases.
I understand Unicode,Asci,Latin,UTF and I have read the Qt Framework documentation
I need to convert QString to QByteArray and vice versa so as not to loose any data while converting

How to accomplish such conversion?

[high_flyer]

I don't think you can, from the simple fact, that QByteArray has non visible ASCII values (or can have).
What you need is not to be able to convert QByteArray to QString, but to apply the functionality you have in QStinrg for your QByteArray data.
As far as I understand it, you will have to implement that your self.

[wysota]

Yes of course it is one of the cases.
I understand Unicode,Asci,Latin,UTF and I have read the Qt Framework documentation
I need to convert QString to QByteArray and vice versa so as not to loose any data while converting

How to accomplish such conversion?

But why exactly do you want this conversion to take place? If you want to xor the string then just do it. Each QChar is a 16 bit value, just xor it with 16 bits of your key and you'll get two 8b values that you can store in the byte array.

QByteArray xorEncrypt(const QString &string, const QByteArray &key){
  QByteArray result;
  int keyIndex = 0;
  for(int i=0;i<string.size();++i){
    quint16 val = string.at(i).unicode();
    char high = key.at(keyIndex++);
    if(keyIndex==key.size()) keyIndex = 0;
    char low = key.at(keyIndex++);
    if(keyIndex==key.size()) keyIndex = 0;
    quint16 keyPiece = ((high & 0xFF) << 8) | (low & 0xFF));
    quint16 encoded = val ^ keyPiece;
    result.append(encoded >> 8);
    result.append(encoded & 0xFF);
  }
  return result;
}

QByteArray xorEncrypt(const QString &string, const QByteArray &key){
  QByteArray result;
  int keyIndex = 0;
  for(int i=0;i<string.size();++i){
    quint16 val = string.at(i).unicode();
    char high = key.at(keyIndex++);
    if(keyIndex==key.size()) keyIndex = 0;
    char low = key.at(keyIndex++);
    if(keyIndex==key.size()) keyIndex = 0;
    quint16 keyPiece = ((high & 0xFF) << 8) | (low & 0xFF));
    quint16 encoded = val ^ keyPiece;
    result.append(encoded >> 8);
    result.append(encoded & 0xFF);
  }
  return result;
}

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Decoding is similar, you just need to reassemble the string.

Of course be aware that xor is a very lousy "cipher" that can be broken within a couple of seconds, especially when encoding data consisting mostly of 0x00:
0x00 xor SECRET = SECRET

The easiest way to break xor is to feed it with a message (either plaintext or ciphertext) consisting of zeroes. Then the key will reveal itself during encryption/decryption.