Signals and Slots questions

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?

Code:

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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.

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

Code:

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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.

Quote:

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Originally Posted by 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?

Code:

---

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

---

---

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:

Code:

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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:

Code:

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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():

Code:

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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:

Code:

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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.

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