Link QVariant to global variable

[jobrandt]

I have list of properties. Each property has a name and a QVariant value. I can access each property over the name(like QSettings).
I want to connect some property to a concrete global variable. If the value of property is changed the global variable should also be changed.
Here is some code to to show what i mean.

// global variable
double xy;  // could be any other type (e.g int,QPoint,QString etc.)
 
class Prop
{
private:
	QString mName;
	QVariant mValue;
	QVariant /*or void?? */ *mPointer; // should point to xy
 
public: 
	void SetPointer(/*Pointer to xy*/) 
	{ 
		mPointer = /*Pointer to xy*/;
	}
 
	void SetGlobalVariabel()
	{
                     // should set xy indirect with mPointer
	    */*Pointer to xy*/ = mValue.value();
	}
};

// global variable
double xy;  // could be any other type (e.g int,QPoint,QString etc.)

class Prop
{
private:
	QString mName;
	QVariant mValue;
	QVariant /*or void?? */ *mPointer; // should point to xy

public: 
	void SetPointer(/*Pointer to xy*/) 
	{ 
		mPointer = /*Pointer to xy*/;
	}
	
	void SetGlobalVariabel()
	{
                     // should set xy indirect with mPointer
	    */*Pointer to xy*/ = mValue.value();
	}
};

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Is this possible? If yes, how can i do this.
There are other ways to change the global variable. But also this way should work.