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Thread: Changing the slot of a signal

  1. #1
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    Default Changing the slot of a signal

    (PyQt5)
    I have my first gui program that is in the VERY rough stages. Here's what it looks like just for reference:
    Screen Shot 2016-06-29 at 13.48.50.jpg
    Here's some heavily abridged code it runs on:

    Qt Code:
    1. class MyWidget(QWidget):
    2. def __init__(self):
    3. super().__init__()
    4. self.main_screen()
    5.  
    6. def main_screen(self):
    7. self.button_1 = RightSideButton("Enter")
    8. # RSB is my own class, to normalize the size of the buttons to 1 inch square on screen, extending QPushButton
    9. self.main_input = QLineEdit()
    10. # sets everything else up
    11.  
    12. self.reset()
    13. self.showMaximized()
    14.  
    15. def reset(self):
    16. # does stuff
    17. self.button_1.clicked.connect(self.run_main)
    18. self.main_input.returnPressed.connect(self.button_1.click)
    19.  
    20. def run_main(self):
    21. # does stuff
    22. self.button_1.clicked.connect(self.run_next) # this line doens't seem to do anything
    23.  
    24. def run_next(self):
    25. # does stuff
    26. self.reset()
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    In this, button_1 is the one on the bottom right. I'm trying to have the program run through different "modes" as it were, where in each mode it does different things when you type something in the main input and hit enter or the button on the lower right.

    It works at first, going through run_main() as it should, but when it gets to the end (line 21) and tries to "change modes" by changing the slot of the button signal, it doesn't work and it just goes back through run_main() if I hit enter in the main input OR click the button. Is there even a way to change the slot of a signal once it's been set?

  2. #2
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    Default Re: Changing the slot of a signal

    Connecting a a new signal/slot does not replace any existing signals/slots. If I understand what you're trying to do, you need to disconnect the signal/slot in run_main after you've connected the clicked signal with the run_next slot, otherwise, next button click, all connected slots will be called, which means your run_main slot would be invoked again, which I suspect is what you're encountering.
    I write the best type of code possible, code that I want to write, not code that someone tells me to write!

  3. #3
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    Default Re: Changing the slot of a signal

    That does seem to be the case, because I put in some print debugging messages to go along with breakpoints, and it does run_next after run_main

    So now to discover how to clear the slots.

  4. #4
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    Default Re: Changing the slot of a signal

    Quote Originally Posted by hamstap85 View Post
    So now to discover how to clear the slots.
    You use the disconnect method instead of the connect method. I don't write python code, but I presume the syntax would be something like:

    Qt Code:
    1. def run_main(self):
    2. # does stuff
    3. self.button_1.clicked.connect(self.run_next)
    4. self.button_1.clicked.disconnect(self.run_main)
    To copy to clipboard, switch view to plain text mode 
    I write the best type of code possible, code that I want to write, not code that someone tells me to write!

  5. #5
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    Default Re: Changing the slot of a signal

    You could also keep a single connection but connect to a slot which then calls the right method depending on your application's state.

    Cheers,
    _

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