Behaves exactly like setValue() otherwise. It returns a QVariant containing a copy of value. In the code, we used QVariant QVariant::fromValue(const T & value). QVariant v = QVariant::fromValue(mClass) Let's look at the following code which want to get the class member from QVariant. Will the QVariant work with custom types such as class?

QVariant with Custom Types (class, struct, etc.) does not guarantee the valid conversionīecause QVariant is part of the Qt Core module, it cannot provide conversion functions to data types defined in Qt GUI, such as QColor, QImage, and QPixmap. The code below is doing serialization and QVariant is being used for the variable v. If you ask for a type that cannot be generated from the stored type, the result depends on the type see the function documentation for details. If you ask for a type that can be generated from the stored type, toT() copies and converts and leaves the object itself unchanged. If you ask for the stored type, they return a copy of the stored object. The methods named toT() (e.g., toInt(), toString()) are const. (Some type()s are multi-valued, for example a string list.) You can find out what type, T, the variant holds, convert it to a different type using convert(), get its value using one of the toT() functions (e.g., toSize()) and check whether the type can be converted to a particular type using canConvert(). Without QVariant, this would be a problem for QObject::property() and for database work, etc.Ī QVariant object holds a single value of a single type() at a time. The QVariant class acts like a union for the most common Qt data types.īecause C++ forbids unions from including types that have non-default constructors or destructors, most interesting Qt classes cannot be used in unions. In this tutorial, we will learn about QVariant.

Qt signal slot custom class