get the last QWidget actived

[SGaist]

Hi,

Can you give more details about that chain of casts ?

[bozo6919]

Hi,

My program has two projects :

• one is a DLL.
• the other an EXE.
  In my EXE, I have to apply a qobject_cast on a class who is contained in my DLL.
  But if I put in this class (in the DLL) the macro Q_OBJECT, my IDE (visual studio 2017) cannot compile the project with an error of linking.

[SGaist]

Is your .dll project also managed with Qt ?

[bozo6919]

Yes, theses projects was made with Qt

[SGaist]

Then there should be no problem with qobject_cast.

[bozo6919]

Yes, but I have problems, and I don't know yet how to resolve them

[SGaist]

What exact problems ?

[bozo6919]

Hi, sorry for my late

This problem for example :

#pragma once

#include <QtCore/qobject.h>

class __declspec(dllexport) LayoutManager : public QObject
{
	Q_OBJECT

public:
	template <class T>T findParent(QObject *child)
	{
		T r = nullptr;

		if (!child)
			return nullptr;
		QObject *parent = child->parent();

		while (parent) {
			r = qobject_cast<T>(parent);
			if (r)
				return r;
			parent = parent->parent();
		}
		return r;
	}
};

And I have this error message :
Error : C2338 : qobject_cast requires the type to have a Q_OBJECT macro

But the macro is here. So instead of qobject_cast, I have to use dynamic_cast

[SGaist]

What type are you looking for ?

[bozo6919]

This is a type who doesn't exist in this project. I use this function in another project

[SGaist]

And is that type a QObject based class with Q_OBJECT in it's declaration ?

@bozo6919 said in get the last QWidget actived:

class __declspec(dllexport) LayoutManager : public QObject

On a side note, Qt provides macros to properly handle the export/import stuff. See here.