BpsVariant Class Reference

Hook up custom variable types and classes in QVariant. More...

#include <bpsvariant.h>

Static Public Member Functions
template<typename T >
static void	registerCompare ()
	Register custom type/class for QVariant equal operator.
template<typename F , typename T >
static void	registerConvertTo ()
	Register custom type for QVariant conversion to other types. More...

Detailed Description

Hook up custom variable types and classes in QVariant.

By hooking up, it is possible to use the compare operator of the class instead of just comparing the value of the data pointers. Also, direct conversion to other known QVariant types is possible.

Limitations given by current QVariant implementation:

• Only same type can be compared.
• Converting in the other direction not possible.

Example usage in a class:

class Complex
{
public:
    Complex(double aReal = 0.0, double aImg = 0.0) : mReal(aReal), mImg(aImg)
    {
        int metaType = QMetaType::type("Complex");
        if (!metaType || !QMetaType::isRegistered(metaType)) {
            metaType = qRegisterMetaType<Complex>();           // register meta type
            BpsVariant::registerCompare<Complex,Complex>();    // needs operator==Complex
            BpsVariant::registerConvertTo<Complex,QString>();  // needs convertTo(QString...)
            BpsVariant::registerConvertTo<Complex,double>();   // needs convertTo(double...)
        } // if
    } // constructor
 
    QString toString() const
    {
        return bStr("{%1,%2}").arg(mReal).arg(mImg);
    } // toString
 
    operator QVariant() const
    {
        return QVariant::fromValue<Complex>(*this);
    } // convert to QVariant
 
    bool operator==(const Complex aOther)
    {
        return qFuzzyCompare(mReal, aOther.mReal) && qFuzzyCompare(mImg, aOther.mImg);
    } // operator==
 
    bool convertTo(QString* aValue, bool* aOk = nullptr) const
    {
        *aValue = toString();
        if (aOk) *aOk = true;
        return true;
    } // convertTo QString
 
    bool convertTo(double* aValue, bool* aOk = nullptr) const
    {
        *aValue = mReal;
        if (aOk) *aOk = true;
        return true;
    } // convertTo double
 
private:
    double mReal;
    double mImg;
};

Usage example:

QVariant v1a(Complex(2.0, 3.0));
QVariant v1b(Complex(2.0, 3.0));
QVariant v2(Complex(4.0, 5.0));
 
qDebug() << "v1a == v1a:" << (v1a == v1a);
qDebug() << "v1a == v1b:" << (v1a == v1b);
qDebug() << "v1a == v2:" << (v1a == v2);
qDebug() << v1a.toDouble() << v1a.toString() << v2;

Member Function Documentation

registerConvertTo()

template<typename F , typename T >

static void BpsVariant::registerConvertTo ( )

inlinestatic

Register custom type for QVariant conversion to other types.

In case a conversion to QString is provided, the QDebug stream output will also work (see output of variable v2 in the example).

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The documentation for this class was generated from the following file:

• bpsvariant.h