Signals and Slots Contd.Qt supports four types of signal-slot connections:With direct connections, the slot gets called immediately when the signal is emitted. The slot is executed in the thread that emitted the signal (which is not necessarily the thread where the receiver object lives).With queued connections, the slot is. 8BiTs 매일 코딩 홈페이지. (Qt) Cross Thread Signal and Slots - 2 Get Code.

One key and distinctive feature of Qt framework is the use of signals and slots to connect widgets and related actions. But as powerful the feature is, it may look compelling to a lot of developers not used to such a model, and it may take some time at the beginning to get used to understand how to use signals and slots properly. However, since version 4.4, we can relay on auto-connections

Qt Send Signal

to simplify using this feature.
Back in the old days, signals and slots connections were set up for compile time (or even run time) manually, where developers used the following sentence:
this is, we stated the sender object's name, the signal we want to connect, the receiver object's name and the slot to connect the signal to.
Now there's an automatic way to connect signals and slots by means of QMetaObject's ability to make connections between signals and suitably-named slots. And that's the key: if we use an appropriate naming convention, signals and slots will be properly connected without the need to write additional code for that to happen. So by declaring and implementing a slot with a name that follows the following convention:
uic (the User Interface Compiler of Qt) will automatically generate code in the dialog's setupUi() function to connect button's signal with dialog's slot.

Qt Signal Slot Different Thread

So back to our example, the class implementing the slot must define it like this:
We then write the method's implementatio to carry on an action when the signal is emitted:

Qt Signal Slot Thread Context

Qt Signal Return Value

In brief, we have seen that by using automatic connection of signals and slots we can count on both a standard naming convention and at the same time an explicit interface for designers to embrace. If the proper source code implements such a given interface, interface designers can later check that everything is working fine without the need to code.