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.

[wysota]

If the global variable was also of type QVariant then this would be easy, but if you want to allow a generic type without QVariant, you have to provide some kind of "handlers" for different types and associate them with each global var. It'd be much easier if you used QVariant

[jobrandt]

Now i have solved the problem with a handler:

// global variable
double xy;  // could be any other type (e.g int,QPoint,QString etc.) 
 
class Prop
{
private:    
   QString mName;    
   QVariant mValue;    
   void *mPointer; // should point to xy 
 
public:
   void SetPointer(void *pointer)     
   {         
      mPointer = pointer;    
   } 
 
   void SetGlobalVariabel() // should set xy indirect with mPointer   
   {                     
		  if (!mPointer) return;
 
	  	switch (mValue.type()) 
		  {
	  	case (QVariant::Double): {
			  *(static_cast<double*>(mPointer)) = mValue.value<double>();
			  break;
			  }
		  case (QVariant::Int): {
			  *(static_cast<int*>(mPointer)) = mValue.value<int>();
			  break;
			  }
		  default:
           ;
		  }
   }
};

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

class Prop
{
private:    
   QString mName;    
   QVariant mValue;    
   void *mPointer; // should point to xy 
   
public:
   void SetPointer(void *pointer)     
   {         
      mPointer = pointer;    
   } 
       
   void SetGlobalVariabel() // should set xy indirect with mPointer   
   {                     
		  if (!mPointer) return;

	  	switch (mValue.type()) 
		  {
	  	case (QVariant::Double): {
			  *(static_cast<double*>(mPointer)) = mValue.value<double>();
			  break;
			  }
		  case (QVariant::Int): {
			  *(static_cast<int*>(mPointer)) = mValue.value<int>();
			  break;
			  }
		  default:
           ;
		  }
   }
};

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SetPointer(&xy) links the QVariant variable to the global variable.
SetGlobalVariable() sets the global variable.

This is not exactly what i wanted but since i only need some types of QVariant it is the fastest way to solve the problem.

A more common solution should be possible if i would know the address(pointer) where QVariant stores the value of the variable.

But at the moment the problem is solved for me.

Thanks for the help.