Converting value read from external file to Bool QVariant

Perdrix

I have an external file created by an earlier version of my code (before I changed to use Qsettings.

As an example consider the following record in the file:

#WS#Software\DeepSkyStacker\FitsDDP|FITSisRAW=0

The new code reads and parses that line and converts Software\DeepSkyStacker\FitsDDP|FITSisRAW to give a QSettings key of "FitsDDP/FITSisRAW", and a QString value for the stuff on the RHS of the = sign in this case "0".

My QSettings for "FitsDDP/FITSisRAW" have this as a bool type.

So my code goes:

                WORKSPACESETTINGITERATOR			it;
		it = findSetting(keyName);
		if (it != m_vSettings.end())
		{
			//
			// In all cases when we enter here the variable "value" will be
			// a QString.
			// We need to convert it to the same type as is currently stored
			//
			QVariant variant(value);
			QVariant::Type type = it->value().type();
			ZASSERT(variant.canConvert(type));
			variant.convert(type);
			it->setValue(variant);
			bResult = true;
		}

I read the current type of the variable using it->value().type() which returns the value 1 (Bool)

and then convert it to type Bool using variant.convert(type);

Unfortunately at this point the value of the QVariant is true NOT false which doesn't seem correct to me!

HELP

Perdrix

@Bonnie said in Converting value read from external file to Bool QVariant:

qDebug() << v;
qDebug() << v.convert(QMetaType::Bool);
qDebug() << v;

Aha! The value of the string showed in the debugger in hover mode as just "0", but it actually contained:

"0\n"

So I was defeated by trailing white space. I see QString::trimmed() in my future :)

Many thanks for your help
David

Christian Ehrlicher

What's the content of 'value' which you're trying to convert to a bool? Why is it a string in the first place?

Perdrix

I thought that was 100% clear from my post the value the QString whose name is value is "0" as that's what was read from the file.

D

Bonnie

I tried below code

QString s("0");
QVariant v(s);
qDebug() << v;
qDebug() << v.convert(QMetaType::Bool);
qDebug() << v;

The output is

QVariant(QString, "0")
true
QVariant(bool, false)

So I think the converting is correct.
Maybe you can also print variant before and after the converting to check its value.

JonB

@Perdrix
As @Bonnie has shown. In the case of converting a QString to a bool, https://doc.qt.io/qt-5/qvariant.html#toBool:

Returns true [...] if the variant has type QMetaType::QString or QMetaType::QByteArray and its lower-case content is not one of the following: empty, "0" or "false"; otherwise returns false.

Perdrix