template compilation problem

[totem]

Hi,

I'm facing a compilation problem : I don't have it with visual studio compiler, but when I try to compile the same code using QtCreator with Linux (and apparently reproduced on Mac), an error appears.

header1.h code :

#ifndef _MY_CLASS1_H_
#define _MY_CLASS1_H_
 
#include <QObject>
 
class MyClass1 : public QObject
{
	Q_OBJECT
 
public :
 
	MyClass1(QObject *parent=0) ;
	virtual ~MyClass1(void) ;
} ;
 
#endif // _MY_CLASS1_H_

#ifndef _MY_CLASS1_H_
#define _MY_CLASS1_H_

#include <QObject>

class MyClass1 : public QObject
{
	Q_OBJECT

public :

	MyClass1(QObject *parent=0) ;
	virtual ~MyClass1(void) ;
} ;

#endif // _MY_CLASS1_H_

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class1.cpp code :

#include "header1.h"
#include "header2.h"
 
MyClass1::MyClass1(QObject *parent)
: QObject(parent)
{
}
 
 
MyClass1::~MyClass1()
{
}

#include "header1.h"
#include "header2.h"

MyClass1::MyClass1(QObject *parent)
: QObject(parent)
{
}


MyClass1::~MyClass1()
{
}

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header2.h code :

#ifndef _MY_CLASS2_H_
#define _MY_CLASS2_H_
 
#include <QObject>
#include <QList>
 
class MyClass2 : public QObject
{
	Q_OBJECT
 
public :
 
	MyClass2(QObject *parent=0) ;
	virtual ~MyClass2(void) ;
 
        template<typename T>
	QList<T*> listOfTypedObjects(void) const ;
} ;
 
template<typename T>
QList<T*>
MyClass2::listOfTypedObjects(void) const
{
	QList<T*> result1 ;
	QList<T*> result2 ;
 
	QList<T*>::const_iterator it ;
	for(it=result1.begin(); it!=result1.end(); it++)
		result2.push_back(*it) ;
 
	return result2 ;
}
#endif // _MY_CLASS2_H_

#ifndef _MY_CLASS2_H_
#define _MY_CLASS2_H_

#include <QObject>
#include <QList>

class MyClass2 : public QObject
{
	Q_OBJECT

public :

	MyClass2(QObject *parent=0) ;
	virtual ~MyClass2(void) ;

        template<typename T>
	QList<T*> listOfTypedObjects(void) const ;
} ;

template<typename T>
QList<T*>
MyClass2::listOfTypedObjects(void) const
{
	QList<T*> result1 ;
	QList<T*> result2 ;

	QList<T*>::const_iterator it ;
	for(it=result1.begin(); it!=result1.end(); it++)
		result2.push_back(*it) ;

	return result2 ;
}
#endif // _MY_CLASS2_H_

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class2.cpp code :

#include "header2.h"
 
MyClass2::MyClass2(QObject *parent)
: QObject(parent)
{
}
 
 
MyClass2::~MyClass2()
{
}

#include "header2.h"

MyClass2::MyClass2(QObject *parent)
: QObject(parent)
{
}


MyClass2::~MyClass2()
{
}

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The error points to MyClass2::listOfTypedObjects method body - and more specifically to the iterator declaration - and tells something like :

line 27 : expected ';' before it

as if It did not recognize QList<T*>::const_iterator definition.

I attached a small example reproducing the problem.
templates.zip

Any idea what I'm missing ?

[high_flyer]

I can't see in your code, when T is getting resolved. (that is, when it gets to be a specific type).
This might also be the problem GCC has.

[totem]

I can't see in your code, when T is getting resolved. (that is, when it gets to be a specific type).
This might also be the problem GCC has.

in fact the template method is not called, that's why I was confused.
Anyway, I think I found a solution, though I did not test it yet : add the keyword typename in front of the iterator declaration

typename QList<T*>::const_iterator it ;

typename QList<T*>::const_iterator it ;

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After all it seems logical, but VS compiler does not complain about this lack.

Edit: adding 'typename' actually fixed the compilation issue. Thanks anyway high_flyer

[high_flyer]

Oh, and in addition, as far as I know, QObjects and templates don't mix well - more like don't mix at all due to the meta object system, that can't handle it.
AFAIK.