I want to passing a variable/function-return as a template argument

[Prmego]

I have a QVariantHash container which stores some objects like QColor, QFont, etc.
but note that I don't know what the container contains I just told you an example of the objects types that the container can contain.
Those objects I'm trying to store them in a setting.ini file.

QSettings setting("setting.ini", QSettings::IniFormat);
QVariantHash options;
options.insert("fontStyle", fontStyleObject); // QFont fontStyleObject;
options.insert("fontColor", fontColorObject); // QColor fontColorObject;

Q_FOREACH(const QVariant &option, options){
        setting->setValue(options.key(option), option.value<option.typeName()>());
}

The problem lies in this part option.value<option.typeName()>().
I want to retrieve each object as before by using the method const char *QVariant::typeName() which returns the type of each object.

Unfortunately, there is an error message error: C2974: 'QVariant::value': invalid template argument for 'T', type expected, because of <option.typeName()> doen't work as a template argument.

Is there any solution to continue and achieve this idea?

[Vinod Kuntoji]

@Prmego ,

Try this, it will work,

Q_FOREACH(const QVariant &option, options){
setting.setValue(options.key(option),options.value(option.typeName()));
}

[jsulm]

@Prmego It cannot work like you want - templates are instantiated at compile time. That means the type T must be known at compile time. If you do

option.value<option.typeName()>();

then the type for T is not known at compile time, so the compiler cannot instantiate the template for unknown type.

[tomma]

Q_FOREACH(const QString &option, options.keys()){
        setting->setValue(option, options.value(option));
}

QSettings takes and returns QVariant, there is no need to overcomplicate things.
QSettings::setValue(const QString &key, const QVariant &value)

If you need to know type of QVariant then you can check QVariant::type()

[Prmego]

@Vinod-Kuntoji : Thanks, but unfortunately, it returns QVariant(Invalid) for each object.

[Prmego]

@jsulm : Thank you, I have known that recently (Templates are instantiated at compile time).
But I have asked my question here to find a solution to that problem.

[Eligijus]

@Prmego

Q_FOREACH(const QVariant &option, options){
if(option.typeName() == "QFont")
        setting->setValue(options.key(option), option.value<QFont>());
if(option.typeName() == "QColor")
        setting->setValue(options.key(option), option.value<QColor>());
}

[Prmego]

@tomma : I think your answer is the most appropriate solution.
I thank you for your response.

[Prmego]

@Eligijus : Thank you, but I think you forget something I wrote in my question, look at the following quote:

Note that I don't know what the container contains I just told you an example of the objects types that the container can contain.

Anyway, I thank you.