What does fromHex do?

[houmingc]

Understand tohex caused number2 to be display as hexadecimal.
qDebug()<<"number2"<<number2.toHex();

What does fromHex do?
QByteArray ba = QByteArray::fromHex("05");

[andre]

[quote]Returns a decoded copy of the hex encoded array hexEncoded. Input is not checked for validity; invalid characters in the input are skipped, enabling the decoding process to continue with subsequent characters.

For example:
@
QByteArray text = QByteArray::fromHex("517420697320677265617421");
text.data(); // returns "Qt is great!"
@
See also toHex().[/quote]

[houmingc]

I seen that post. in layman terms please.
Why is it used & how to use it?

[andre]

If you have a byte array (a bunch of raw data, really) that you want to make fit for display as text, you can encode it as hexadecimal values using QByteArray::toHex(). That will mean that every byte is encoded as two characters from the range 0-9A-F.

QByteArray::fromHex() does the reverse: it interprets a byte array as a set of characters where every two characters together encode a single byte again. Any character in the input other than those in the range 0-9A-F is just skipped.

Note that the character range 0-9A-F are characters, that is, values 48-57 and 65-70.

Example:
The QByteArray containing these values (as 3 bytes): 256, 77, 23
Written in hex, that would be FF 4D 17 (that is: 3 values, written as 6 characters)
would after hex encoding it would then be: (as 6 bytes (chars)): 70, 70, 52, 68, 50, 55

If you'd print that using qDebug(), or convert it into a QString, it would read "FF4D17".