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  4. How to link a bool variable to a push button in c++ qt?

How to link a bool variable to a push button in c++ qt?

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  • J JonB
    23 Sept 2020, 08:59

    @nanor
    You seem to be relying on the names of your slots being auto-connected to signals. Put in debug messages to see whether your slots are being called at all?

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    nanor
    wrote on 23 Sept 2020, 09:08 last edited by
    #3

    @JonB Thank you for replying. I don't understand exactly what to do. Do you mean I must run the code in debugging mode and see if there are errors or not?
    I ran the code in debugging mode and there were no errors.

    J 1 Reply Last reply 23 Sept 2020, 09:13
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    • N nanor
      23 Sept 2020, 09:08

      @JonB Thank you for replying. I don't understand exactly what to do. Do you mean I must run the code in debugging mode and see if there are errors or not?
      I ran the code in debugging mode and there were no errors.

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      JonB
      wrote on 23 Sept 2020, 09:13 last edited by JonB
      #4

      @nanor
      Put lines like qDebug() << "Got to this line (1)" (you may need #include <QDebug> at the top of your file) into your on_pushButton_clicked() & on_pushButton_2_clicked() slots. When you run from Qt Creator, do you see output appearing (I think it's in the "Application Output" tab at the bottom)?

      N 1 Reply Last reply 23 Sept 2020, 09:27
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      • J JonB
        23 Sept 2020, 09:13

        @nanor
        Put lines like qDebug() << "Got to this line (1)" (you may need #include <QDebug> at the top of your file) into your on_pushButton_clicked() & on_pushButton_2_clicked() slots. When you run from Qt Creator, do you see output appearing (I think it's in the "Application Output" tab at the bottom)?

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        nanor
        wrote on 23 Sept 2020, 09:27 last edited by
        #5

        @JonB I put qDebug() << "1" into on_pushButton_clicked() and qDebug() << "2"; into on_pushButton_2_clicked() . I see outputs when I run the code.
        The code works well (after clicking on the pushButton , the labels become unhide and after clicking the pushButton_2(which is related to the multiply of two numbers) it works well too).
        The only part that does not work, is when I click on the pushButton for the second time to hide the labels again(When I click on the pushButton for the second time, all the labels remain, but my goal is to hide them again, but nothing happens).

        J 1 Reply Last reply 23 Sept 2020, 09:33
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        • N nanor
          23 Sept 2020, 09:27

          @JonB I put qDebug() << "1" into on_pushButton_clicked() and qDebug() << "2"; into on_pushButton_2_clicked() . I see outputs when I run the code.
          The code works well (after clicking on the pushButton , the labels become unhide and after clicking the pushButton_2(which is related to the multiply of two numbers) it works well too).
          The only part that does not work, is when I click on the pushButton for the second time to hide the labels again(When I click on the pushButton for the second time, all the labels remain, but my goal is to hide them again, but nothing happens).

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          JonB
          wrote on 23 Sept 2020, 09:33 last edited by
          #6

          @nanor said in How to link a bool variable to a push button in c++ qt?:

          When I click on the pushButton for the second time, all the labels remain, but my goal is to hide them again, but nothing happen

          So look at your code in on_pushButton_clicked() where you call setVisible(true) on each widget. So why do you expect them to disappear? What could you write there instead of true there to make it work as you want?

          N 1 Reply Last reply 23 Sept 2020, 09:44
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          • J JonB
            23 Sept 2020, 09:33

            @nanor said in How to link a bool variable to a push button in c++ qt?:

            When I click on the pushButton for the second time, all the labels remain, but my goal is to hide them again, but nothing happen

            So look at your code in on_pushButton_clicked() where you call setVisible(true) on each widget. So why do you expect them to disappear? What could you write there instead of true there to make it work as you want?

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            nanor
            wrote on 23 Sept 2020, 09:44 last edited by
            #7

            @JonB Yes, that's right. But I wrote bForButton = !bForButton; before writing the setvisible(true) for the items in on_pushbutton_clicked(). As in the constructor I wrote bForButton = false, I thought that for the second time clicking on the pushbutton, the boolian value turns into false again and all of the elements become hide again.

            B J 2 Replies Last reply 23 Sept 2020, 09:51
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            • N nanor
              23 Sept 2020, 09:44

              @JonB Yes, that's right. But I wrote bForButton = !bForButton; before writing the setvisible(true) for the items in on_pushbutton_clicked(). As in the constructor I wrote bForButton = false, I thought that for the second time clicking on the pushbutton, the boolian value turns into false again and all of the elements become hide again.

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              Bob64
              wrote on 23 Sept 2020, 09:51 last edited by
              #8

              @nanor but what is using bForButton?

              Actually it is better not to use this flag at all. Can you query the button's current visibility?

              N 1 Reply Last reply 23 Sept 2020, 10:12
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              • N nanor
                23 Sept 2020, 09:44

                @JonB Yes, that's right. But I wrote bForButton = !bForButton; before writing the setvisible(true) for the items in on_pushbutton_clicked(). As in the constructor I wrote bForButton = false, I thought that for the second time clicking on the pushbutton, the boolian value turns into false again and all of the elements become hide again.

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                JonB
                wrote on 23 Sept 2020, 09:57 last edited by JonB
                #9

                @nanor said in How to link a bool variable to a push button in c++ qt?:

                But I wrote bForButton = !bForButton

                Think about how/why that then messes things up from then on, because you have changed the value of the bForButton value in doing so. You must not change that variable itself. Hint: it's OK to pass !bForButton as an expression/parameter, but not to go bForButton = !bForButton.... Or, you could choose to go down @Bob64's "current widget visibility" route, though that's more code to write/maintain.

                N 1 Reply Last reply 23 Sept 2020, 10:23
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                • B Bob64
                  23 Sept 2020, 09:51

                  @nanor but what is using bForButton?

                  Actually it is better not to use this flag at all. Can you query the button's current visibility?

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                  nanor
                  wrote on 23 Sept 2020, 10:12 last edited by
                  #10

                  @Bob64 Actually I used bForButton to hide and unhide the labels by clicking on push buttons (For the first time clicking on the push_button, I want to unhide the labels, for the second time clicking on the push_button I want to hide them again, for the third time the goal is unhiding them again...).
                  I set bForButton=false for hiding and bForButton=!bForButton for unhiding them.

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                  • J JonB
                    23 Sept 2020, 09:57

                    @nanor said in How to link a bool variable to a push button in c++ qt?:

                    But I wrote bForButton = !bForButton

                    Think about how/why that then messes things up from then on, because you have changed the value of the bForButton value in doing so. You must not change that variable itself. Hint: it's OK to pass !bForButton as an expression/parameter, but not to go bForButton = !bForButton.... Or, you could choose to go down @Bob64's "current widget visibility" route, though that's more code to write/maintain.

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                    nanor
                    wrote on 23 Sept 2020, 10:23 last edited by
                    #11

                    @JonB I put setVisible(bForButton) instead of setVisible(true) for the elements into on_pushButton_clicked() slots and my code worked well. Thank you so much. I really appreciate your help.

                    J P 2 Replies Last reply 23 Sept 2020, 10:37
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                    • N nanor
                      23 Sept 2020, 10:23

                      @JonB I put setVisible(bForButton) instead of setVisible(true) for the elements into on_pushButton_clicked() slots and my code worked well. Thank you so much. I really appreciate your help.

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                      JonB
                      wrote on 23 Sept 2020, 10:37 last edited by
                      #12

                      @nanor
                      Well done for figuring this for yourself! Hopefully you can see now exactly why that is indeed the right thing to do!

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                      • N nanor
                        23 Sept 2020, 10:23

                        @JonB I put setVisible(bForButton) instead of setVisible(true) for the elements into on_pushButton_clicked() slots and my code worked well. Thank you so much. I really appreciate your help.

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                        Pablo J. Rogina
                        wrote on 23 Sept 2020, 12:07 last edited by
                        #13

                        @nanor said in How to link a bool variable to a push button in c++ qt?:

                        my code worked well

                        great, so please don't forget to mark your post as solved!

                        Upvote the answer(s) that helped you solve the issue
                        Use "Topic Tools" button to mark your post as Solved
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                        23 Sept 2020, 10:37

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