The connection mechanism uses a vector indexed by signals. But all the slots waste space in the vector and there are usually more slots than signals in an object. So from Qt 4.6, a new internal signal index which only includes the signal index is used. While developing with Qt, you only need to know about the absolute method index.

Say I a widget A and a vector of widget B's (the number of which is only known at runtime and is dynamic)

Qt Signal Slot Mapper App

1. I hope these articles have demystified signals and slots, and that knowing a bit how this works under the hood will help you make better use of them in your applications. Woboq is a software company that specializes in development and consulting around Qt and C.
2. Qt allows us to connect multiple signals to the same signal or slot. This can be useful when we provide the user with many ways of performing the same operation. Sometimes, however, we would like the slot to behave slightly differently depending on which widget invoked it. In this article we.
3. QtCore.SIGNAL and QtCore.SLOT macros allow Python to interface with Qt signal and slot delivery mechanisms. This is the old way of using signals and slots. The example below uses the well known clicked signal from a QPushButton. The connect method has a non python-friendly syntax. It is necessary to inform the object, its signal (via macro.

I would like a signal / slot relationship between A and all B's, such that I can choose the slot of which of the widget B's recieves the signal.

i.e some sort of emit widgetASignal (slotOfWidgetB_X, double amount)

Now, I am aware of QSignalMapper, but as far as I can tell that is for the counterpart of what I would like i.e QSignalMaper would be vector of widget B's, one of which sends a signal, and widget A slot recieves the signal and can work out which of widget B's it came from.

I want to do the opposite here, and emit a signal defined in widgetA and it get to only one of the instances of widgetB.

Any help much appreciated.

Qt Signal Slot Mapper Free

I try to understand the QSignalMapper and to do some proper work with it but there are some pieces of code I see almost everywhere but don't really get:

Qt Signal Slot Mapper App

@connect(button, SIGNAL(clicked()), signalMapper, SLOT(map()));@

What is the
@SLOT(map())@

used for and by what could it be replaced with? Or is it necessary to have exactly that method here?

If I'm not completely wrong 'connect(...)' connects a Signal to either a slot or a signal. And if my preferred signal hasn't got the parameters I need in the Slot I use the QSignalMapper?

Qt Signal Slot Mapper Bot

With using
@signalMapper->setMapping(button, const QString &);@

Qt Signal Slot Mapper Software

I 'pretend' (or better: QT behaves as) the signal @clicked()@

had a QString-paramter, right?

Most tutorials have in the end of their snipplets another line with this ominous map()-Function:

@connect(signalMapper, SIGNAL(mapped(const QString &)), this, SIGNAL(clicked(const QString &)));@

I get the first paramter. signalMapper is used because it's the Object of action, right?
But how and why did the map()-function become a Signal too? (Usually this line has no comments unfortunately).
The third is clear, that's the parent...
But since when does the clicked-Signal really have a QString as parameter...?

Qt Signal Slot Mapper Tool

I'd be thankful if someone could help me with understanding that...

As sources I used among others:
http://developer.nokia.com/community/wiki/Mapping_signal_via_signalMapper
http://www.java2s.com/Code/Cpp/Qt/QSignalMapper.htm

And this:
http://qt-project.org/doc/qt-4.8/qsignalmapper.html#setMapping
Which has the best explanation but still the lines I mentioned are unclear...