3.5. Signals and slots

Now the widgets are implemented and the layout is arranged the final thing we need to do in the design stage of the form is to create the signal/slot connections. To do this manually requires a connect() function but Qt Designer provides a simple yet effective solution. To create the signal/slot connections we need to use the connecting tool. To do this either select the icon (it looks like a red arrow going into a blue square) or select Tools-> Connect Signals/Slots from the menu. To create a connection, click on the form on the widget that is going to be dealing with the slot, drag the line off the form and release the mouse button.

Let's deal first with the Create! button. Click first on the Connect Signal/Slot icon or select it from the Tools menu or use the shortcut which is the F3 key. Then click on the Create! button with the crosshair and drag the line off the form completely. When you have released the mouse button you will see the connections tool shown in Picture 9.

What we want to do is to create a slot that will create our signature when the user clicks on the button. The signal will be clicked() (you may choose among five signals for a QPushButton) and we need to create the slot then make the connection.

To create the slot we need to click on the "Edit Slots" button. The slot creation box then appears. See Picture 9. Now click on the New Slot button and a slot will appear in the box. Instead of new_slot() rename it to slotCreateSig() and leave the access specifier as public. When you click on OK you will be returned to the connections box and you will see your new slot in the Slots section of the box.

To make a connection you simply select the appropriate signal (which is clicked() in our case) and then select the slot (which is our new slot slotCreateSig()). When you have selected both signal and slot you will see the connection made at the bottom of the screen. After you are finished click OK.

Repeat the procedure for the Cancel button by using the clicked() signal and the reject() slot. You are now done with the signals and slots.