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How to automatically emit a signal



  • Hello,
    I was wondering if there was a way to automatically emit a signal. So instead of, lets say, you clicking a button to calculate something, that instead once you finish editing it, it automatically runs the signal.
    Is there a possible way to do this?


  • Moderators

    @rocklionmba said in How to automatically emit a signal:

    that instead once you finish editing it, it automatically runs the signal.

    What is "it"? Finish editing what? Can you give a specific example of what you're trying to do?
    Signals are just regular c++ functions so whatever you can do with regular c++ functions you can do with signals.



  • So I have a list of items that all need to be filled out ( Unit of measure, number of coats, material type, quantity, paint type) before any calculations can be done. What I want to do is to have it where once all of them are filled out, it automatically sends the signal to the slots where it calculates it.


  • Moderators

    @rocklionmba said in How to automatically emit a signal:

    it automatically sends the signal to the slots where it calculates it

    So... still, what is "it"? Who fills these items? A user through some ui or some part of your code?



  • it would be the list of items that's on the ui that the user fills out.



  • It sounds like the goal is to have something happen after several fields are filled out.

    eg Send an email after a recipient, subject, and body are entered. These can be done in any order, but a message should only be sent when all three are present.

    There's no automatic signal for an arbitrary multi-input use case, but it's easy enough to create one. Create a function that checks each input and emits a signal (or starts the calculation directly) when a valid configuration exists. void checkValid() { if (input1.isValid && input2.isValid) action(); }

    Find a change signal for each input, and call the validation function.

    Item {
        id: input1
        property bool isValid
        ...
        onChanged: checkValid()
    }
    
    Item {
        id: input 2
        property bool isValid
        ...
        onChanged: checkValid()
    }
    


  • You have to do something to emit the signal, even if you are emitting the signal in the constructor,the constructor has to be called.

    Go to event definition,
    Type emit Your signal();
    It will automatically emit the signal when the event is occurred


  • Lifetime Qt Champion

    @rocklionmba

    How do you know " once you finish editing" ?
    How will app know user is finished ?


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