How to use QDir(); to get a path " with native separators"

ademmler

Because a day - here in the forum - i got this informations:
"Qt use "/" as path separator for all OS.
QDir::separator will only be used in QDir::toNativeSeparators."

"While you are using Qt path functions you should always use /, and that is what they will return to you. If you want the native separators QDir has to/fromNativeSeparartors(), but these should only be used if passing to something external, like an OS command."

Hence for me it meant - never use "QDir::separator" it is Qt internal only ....

What I know get is better to use something like this example:

QString mypath =  QStandardPaths::writableLocation(QStandardPaths::DesktopLocation) + QDir::separator() + "my folder";

Thank you very much for making it more clear.

ademmler

@Christian-Ehrlicher said

This is wrong for the arguments you pass to the process - Qt will not modify them in any way.

But it will add "spaces" between all argument "peaces".

Wich leads into this to be correct:
arguments << "-opiton1" << "-ringthebell" << "yes" ... ;

JonB

@ademmler said in How to use QDir(); to get a path " with native separators":

QString mypath = QStandardPaths::writableLocation(QStandardPaths::DesktopLocation) + QDir::separator() + "my folder";

For anyone coming across this: As per the article referenced earlier, this is precisely the wrong place to use QDir::separator().

ademmler

@JonB thx for responding.
Maybe I am mistaken - but from the discussion above I got the recommendations to use QDir::separator(). Now I am not sure which answer is the correct one.

Pls see above first comment from @Christian-Ehrlicher

Cobra91151

@JonB @ademmler

I have checked it on Windows, this path will work C:/test/path\test.exe even thought it is wrong. So, this code QString myPath = QStandardPaths::writableLocation(QStandardPaths::DesktopLocation) + QDir::separator() + "my folder"; in your case:

QStandardPaths::writableLocation(QStandardPaths::DesktopLocation) will have "/" and
QDir::separator() + "my folder" will have "\my folder".

It will work, but the path is not correct. Instead, there are a lot of options we can do here.
QString myPath = QStandardPaths::writableLocation(QStandardPaths::DesktopLocation).replace("/", "\\") + "\\" + "my folder";
QString myPath = QStandardPaths::writableLocation(QStandardPaths::DesktopLocation).replace("/", "\\") + "\\my folder";

Or

QString myPath = QDir::toNativeSeparators(QStandardPaths::writableLocation(QStandardPaths::DesktopLocation).append("/") + "my folder");

QString myPath = QDir::toNativeSeparators(QStandardPaths::writableLocation(QStandardPaths::DesktopLocation).append("\\") + "my folder");

QString myPath = QDir::toNativeSeparators(QStandardPaths::writableLocation(QStandardPaths::DesktopLocation) + "/" + "my folder");

QString myPath = QDir::toNativeSeparators(QStandardPaths::writableLocation(QStandardPaths::DesktopLocation) + "\\" + "my folder");

QString myPath = QDir::toNativeSeparators(QStandardPaths::writableLocation(QStandardPaths::DesktopLocation) + QDir::separator() + "my folder");

The path should contain all "/" or "\" to be correct.
All, these paths will return: "C:\\Users\\username\\Desktop\\my folder" and it is valid and correct for Windows, so you can use it to build paths and display to the user. The QDir::toNativeSeparators() method will display the correct "/" or "\" depending on the current OS, and will fix the path issue with QDir::separator().

JonB

@Cobra91151
That's a long answer! :)

Yes, the issue will show up under Windows only. C:/test/path\test.exe is the kind of thing that will result from using QDir::separator(). Which looks wrong, and may (or may not) cause problems.

The point is to just use / while passing a path around in Qt code. So

QString mypath = QStandardPaths::writableLocation(QStandardPaths::DesktopLocation) + "/my folder";

would be best.

You only need QDir::separator() or toNativeSeparators() when you're e.g. passing to OS or printing.

JKSH

@ademmler said in How to use QDir(); to get a path " with native separators":

Maybe I am mistaken - but from the discussion above I got the recommendations to use QDir::separator(). Now I am not sure which answer is the correct one.

Pls see above first comment from @Christian-Ehrlicher

@Christian-Ehrlicher only said that you should use native separators when writing the path to an external non-Qt process.

In your example, you are not writing the path to an external process. You are building up a path inside Qt. So, QDir::separator() is not appropriate here.

The correct way to build your path in a cross-platform way is QString mypath = QStandardPaths::writableLocation(QStandardPaths::DesktopLocation) + "/my folder"; like @JonB said.

ademmler

@Christian-Ehrlicher @Cobra91151 @JonB @KroMignon and all the others:

This had been a very longish task - but I am glad about it - because it demystified some obstacles for me.
Somehow QProcess(); and QStandardPaths(); got mixed up - but that was very good for some reason.

Thx again - which answer shall I mark as the solution now? You ALL have been very helpful.

Another question came up into my mind. Whats about using QFile::copy(); function.
Does this take care of platform depended details (in path names) automatically ?

QString targetFile(myFolder.absolutePath() + "/" + base + "." + ext);
QFile sourceFile(inputFile);
bool    ok = sourceFile.copy(targetFile);

aha_1980

Hi @ademmler,

Another question came up into my mind. Whats about using QFile::copy(); function.
Does this take care of platform depended details (in path names) automatically ?

Every Qt API takes forward slashes as separator. You only need native separators when you display a path to the user or when you pass it to some thirdparty API. (Side node: even the Windows API allows forward slashes in many cases).

So yes, QFile::copy takes care for the platform details itself.

Regards

ademmler

@aha_1980 thank you for proving this