Signals and Slots questions

[Janek]

1) I have 2 classes, first is MyForm, and second classTwo. MyForm have private object of type classTwo named objTwo - Is that a good idea? or better to create both of it in main.c as coexistent?

2) In MyForm constructor I try to connect SIGNAL from MyForm to SLOT from classTwo - it's not working, why?

connect(widget.buttonX, SIGNAL(clicked()), objTwo, SLOT(slotX(widget.edit->text())));

connect(widget.buttonX, SIGNAL(clicked()), objTwo, SLOT(slotX(widget.edit->text())));

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As a workaround I declared new SLOT in MyForm which call objTwo.slotX() - this way it works, but Im sure this is bad practice, or isn't it?

The real problem comes when I want to connect SIGNAL from classTwo to MyForm class (in MyForm constructor). The only way I see is to cross include class headers, but I do want to make it properly, so obviously i miss something, as cross including is bad practice?

I need to send something to classTwo from MyForm and then wait for signal to read answer back.

Please help.

[squidge]

The SLOT can only contain the function signature. It can not accept arguments.

connect(widget.buttonX, SIGNAL(clicked()), objTwo, SLOT(slotX()));

connect(widget.buttonX, SIGNAL(clicked()), objTwo, SLOT(slotX()));

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If you check the output window, you will notice an error message being printed with your version.

[faldzip]

1) I have 2 classes, first is MyForm, and second classTwo. MyForm have private object of type classTwo named objTwo - Is that a good idea? or better to create both of it in main.c as coexistent?

2) In MyForm constructor I try to connect SIGNAL from MyForm to SLOT from classTwo - it's not working, why?

connect(widget.buttonX, SIGNAL(clicked()), objTwo, SLOT(slotX(widget.edit->text())));

connect(widget.buttonX, SIGNAL(clicked()), objTwo, SLOT(slotX(widget.edit->text())));

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in SIGNAL() and SLOT() macros you give a signature of a method so the name of a method an type names of arguments, for example:
when you have class:

class A : public QObject
{
    Q_OBJECT
public:
    A(QObject *parent = 0);
public slots:
    void myMethod(int a, const QString str);
};

class A : public QObject
{
    Q_OBJECT
public:
    A(QObject *parent = 0);
public slots:
    void myMethod(int a, const QString str);
};

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and you want to connect some signal to the slot myMethod you have to write it like this:

SLOT(myMethod(int, QString))

SLOT(myMethod(int, QString))

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as you see just names of types, so you can't pass any arguments to slots in a connect() statement.
whats more you can't connect signal with no arguments (like clicked()) with a slot which has arguments, in general, you can't connect signal with less arguments then slot which you connect to.

So in your situation solution looks like:
1. Make a slot with no arguemnts, lets say slotClicked()
2. connect with signal clicked():

connect(widget.buttonX, SIGNAL(clicked()), objTwo, SLOT(slotClicked()));

connect(widget.buttonX, SIGNAL(clicked()), objTwo, SLOT(slotClicked()));

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3. in slotClicked() do something with that thing what you want.
4. but I dont know why you have a slot in different class to process text from a lineEdit() in different class... maybe make that slot in MyForm like this:

void MyForm::slotClicked()
{
    objTwo->doSomething(widget.edit->text());
}

void MyForm::slotClicked()
{
    objTwo->doSomething(widget.edit->text());
}

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that would be the easiest way.


P.S. Ohh and of course try reading some documentation and examples before trying to code, because all I said is written there with more examples and more clearly.

[Janek]

Thank You very much, that clears up a lot, and of course I have to read a lot more about Qt