Small problem with a log file

artwaw

@bask185 QIODevice::WriteOnly implies truncate of the file. You should open with QIODevice::Append instead - that would just... well... append new data at the end of the file.

jsulm

@bask185 To add to @artwaw : why don't you keep the file open? Opening and closing it for each incoming byte sounds like a huge waste of resources.

VRonin

Side note: you should also include the QIODevice::Text flag

bask185

I find it vague that file.open() can actually deletes the content rather than...just open it when given the wrong argument.

Regardless I succeeded:

Bullseye set at 6.33333 7.33333
<< 80
<< 3
0x80 command case 3
<< 37
Bullseye set at 7.33333 7.33333
<< 80
<< 3
0x80 command case 3
<< 38
Bullseye set at 8.33333 7.33333

In the setup I open the file with Write Only and close it so it becomes.. empty :D

But the output is almost the exact same as qDebug. So tnx. I'd like to mark your answer as the correct one, but one can only mark his own ;)

bask185

@VRonin said in Small problem with a log file:

Side note: you should also include the QIODevice::Text flag

If you say something like: "you should do...". Arguments 'why' are not redundant. Not long ago I held a short speech about it ;) and I came across a nice saying a few days ago: "Give a man a fish and you feed him one day, teach a man how to fish and you feed him for his life"

Right now I have a perfectly fine working log file, so I don't feel like including something called 'Text flag' ;)

VRonin

@bask185 said in Small problem with a log file:

"Give a man a fish and you feed him one day, teach a man how to fish and you feed him for his life"

that's what the docs are for. it takes 5 seconds to Google QIODevice::Text

@bask185 said in Small problem with a log file:

Right now I have a perfectly fine working log file, so I don't feel like including something called 'Text flag' ;)

As long as you don't care about newlines.

bask185

@jsulm said in Small problem with a log file:

@bask185 To add to @artwaw : why don't you keep the file open? Opening and closing it for each incoming byte sounds like a huge waste of resources.

Now you mention it... I turned it off but I have another question.

I would like to write data to the log also in other functions but it is a local variable. I tried working with the header file making it more global but I could not get it to work. I also tried

QFile log("logboek.txt");
QTextStream LOG(&log);
LOG  << cAsHex << " >>";

in other functions, but no luck :(

jsulm

@bask185 Implement a class which handles the logging. This class then creates a private static QFile instance and provides public static methods to write logs. Be careful if you use different threads - then you will need to serialize log writing.

bask185

@VRonin said in Small problem with a log file:

@bask185 said in Small problem with a log file:

"Give a man a fish and you feed him one day, teach a man how to fish and you feed him for his life"

that's what the docs are for. it takes 5 seconds to Google QIODevice::Text

@bask185 said in Small problem with a log file:

Right now I have a perfectly fine working log file, so I don't feel like including something called 'Text flag' ;)

As long as you don't care about newlines.

I do care about newlines alot, that is why add them like: LOG << "\nText to translate : "
I've googled and read about it but I am not getting the usage for me, from what I understand it is a windows thingy and it is used for reading files. It sets \r\n to \n for use with C++.

bask185

@jsulm said in Small problem with a log file:

you will need to serialize log writing

You mean working with connects and signals? when class X emits a signal to mainwindow with a string so mainwindow can puts the string in the log using the log-class??

VRonin

@bask185 said in Small problem with a log file:

it is a windows thingy

Mainly yes

and it is used for reading files

Mainly no

From http://doc.qt.io/qt-5/qiodevice.html:

When reading, the end-of-line terminators are translated to '\n'. When writing, the end-of-line terminators are translated to the local encoding, for example '\r\n' for Win32.

That means that \n will be converted to "\r\n" on windows automatically if you add | QIODevice::Text to the open argument

jsulm

@bask185 No, I did not write anything about signals/slots. I mean a class which manages the log writing. There is no need to do it in main window. Just provide static methods:

class Logger
{
public:
    static void log(const QString &text);
private:
    static QFile logFile;
};
...
Logger::log("Some text");