[Solved] Slot inheritance problem despite Q_Object Macro

fant

Hello,

Currently I have a strange problem with slot inheritance. In other forums this problem will talked, too, but it doesn't help me.

At first, I have the abstract superclass (non-essential things I removed):

@class ToyObject {

    Q_OBJECT

    Q_PROPERTY(QString _name READ getName WRITE setName)

public:
    explicit ToyObject(QObject *parent = 0);

protected:
    QString _name;

public slots:
    void setName(QString val) { _name = val; }

    //....

};@

Then my subclass (overwrites the abstract virtual method, that not showed here):

@class GCharacter : public ToyObject {

    Q_OBJECT

public:
    explicit GCharacter(QObject *parent = 0);

    //....

};@

No I used the polymorphism in an other class called OInspector. In header file I declared following methods:

@
void defaultPreparation(ToyObject *to);

void prepare(GCharacter *gCharacter);
@

And implements this:

@
void OInspector::prepare(GCharacter *gCharacter){

defaultPreparation(gCharacter);

//connection to another Slot of GCharacter, that works
QSpinBox *spinFram = createSpinner();
connect(spinFram, SIGNAL(valueChanged(int)), gCharacter, SLOT(setNumOfFrames(int)));

}

void OInspector::defaultPreparation(ToyObject *to){

_nameEdit = new QLineEdit(to->getName(), this);
connect(_nameEdit, SIGNAL(textChanged(QString)), to, SLOT(setName(QString)));

}
@

When I run the application, I get the following warning code:

bq. QObject::connect: No such slot GCharacter::setName(QString) in ...

But GCharacter should inherit the slot from ToyObject, or not? In QtCreator I can call the inherited method without problems.

Thanks for help.

JKSH

Hi,

[quote]@class ToyObject {
...@
...
GCharacter should inherit the slot from ToyObject, or not?[/quote]Yes, it should inherit the slot from ToyObject, if you do the following:

Make sure ToyObject publicly inherits QObject

Make sure you declare both ToyObject and GCharacter in a .h file, not a .cpp file

Run qmake

Recompile your project

fant

Yes it does. ToyObject is a subclass of ISerializable custom class, which inherit from QObject.
Yes, both are in a headerfile declared.

3.+4. Done. But nothing changes.

frankiefrank

I just wanted to iterate what JSKH wrote, is this public inheritance? i.e. your class headers look like

@
class ToyObject : public ISerializable
@

and

@
class ISerializable : public QObject
@
?

hskoglund

Hmm interesting! Just guessing:
perhaps the class inheritance stuff works better if you switch to Qt5-flavored connects, i.e. instead of:
@connect(_nameEdit, SIGNAL(textChanged(QString)), to, SLOT(setName(QString)));@

you try
@connect(_nameEdit, &QLineEdit::textChanged, to, &ToyObject::setName);@

fant

Yes, it is public inheritance, too. In any case.. checked.

hskoglund: You are a genius! It works! :)

So my conclusion:
If you want to work with inherited slots in Qt 5, use the new signal-slot-syntax. Apart from that, I like more the old syntax - the reason follows:
If I connect for example a QComboBox with another object and want to use the signal currentIndexChanged, there are two possible methods (with Integer or QString argument). So the compiler has a problem to decide, which signal is wanted. I have to explicitly tell the compiler the correct functions address:

@
connect(combobox,
static_cast<void (QComboBox::*)(int)>
(&QComboBox::currentIndexChanged),
object,
&MyObjectClass::workWithData);
@

Here some other references for people who have a similar problem:
"New Signal Slot Syntax":http://qt-project.org/wiki/New_Signal_Slot_Syntax
"New Signal Slot Syntax with QComboBox":http://qt-project.org/forums/viewthread/21513

Thank you all for help. :)