How to Use Classes derived from QObject to send signals and have slots

Aethalides

Hi

I have been trying to have a class called Tool that derives from QObject and declares several slots.

I my QMainWindow class (TheClass), I am trying to use that class.

For instance TheClass has a private member:

@private: Tool* TheTool;@

Now when it comes to connect to signals from Tool, I do in the constructor of TheClass:

@connect(TheTool,SIGNAL(theToolSignal),this,SLOT(myToolSlot()));@

Which compiles fine, but when I run it, I get the message

bq. QObject::connect: Cannot connect (nulll)::theToolSignal to TheClass::myToolSlot()

Which seems to indicate that TheTool is not instantiated.

Yet, when I make a call to a member function

@TheTool->member()@

I see from its qDebug() output that it is being called

I have read the notes on the QObject class and that it has a Q_DISABLE_COPY macro which means that implied or explicit assignments won't work and that one cannot instantiate the QObject?

My question for you is then:

How can I modify my code so that I can have a class derived from Q_Object that uses Signals and Slots, and then use that class from another class?

Zlatomir

First make sure that the connect statement is after the line: TheTool = new Tool(); and also at the connect you are missing a pair of parenthesis: @SIGNAL(theToolSignal () )@

Aethalides

Hi

Yes, I transcribed the signal wrong in this question.

However, the problem I have is that when I do use new, the linker starts whinging at me:

bq. in function Tool::Tool()': Tool.h:77: undefined reference to vtable for Tool::Tool'

Zlatomir

-Did you include the header file where the Tool class is declared?-

LE: Make sure that Tool class has Q_OBJECT macro, if it doesn't add it and than run qmake and than build your project.

Aethalides

Hi

I finally figured it out, your mentioning the Q_OBJECT macro again made me check and lo, I did not include the "tool.moc" file.

Interestingly enough, it is not created by my cmake either even though qt4_automoc is fed both the tool as well as the MyClass

I did a moc ../Tool.h > tool.moc in my build directory after appending the include "tool.moc" line in my tool.cpp file, then make and voila! it is compiling!

Thank you, you're a star :)

Aethalides

FYI; getting the cmake to build the moc for the tool as wel was as simple as adding a line

@set(myCoolProject_H tool.h myclass.h)@

In addition to having these lines:

@QT4_WRAP_UI(myCoolProject_H ${myCoolProject_GUI} )

qt4_automoc(${myCoolProject_SRCS})@