[SOLVED]setText not working



  • hello,

    I have a rally noob question here, and its that setText is not working. for example"

        connect(pushButton1, SIGNAL(clicked()), 
                      lineEdit, SLOT(setText(QString("1"))));
    

    it then underlines the line red saying that it expectd a semicolon but got a parenthesis. I checked all the brackets and they seem to line up, and it happens to be the "1" in the setText that causes the problem. any help?


  • Moderators

    You've got a wrong idea of how a signal-slot connection works. The slot parameter is taken from a matching signal argument if it has one, not from you directly.

    For example if there is a signal somethingHappened(int foo) then a slot doSomething(int bar) will receive the parameter from the signal: connect(senderObject, SIGNAL(somethingHappened(int)), receiverObject, SLOT(doSomething(int))).

    So in short you can't pass an argument (QString("1")) at a connection site.

    On the other hand there are a few more connect()overloads that don't take SIGNAL and SLOT macros. For example you can connect a lambda like this:

    connect(pushButton1, &QPushButton::clicked, [=]{ lineEdit->setText(QString("1"); });
    


  • but isn't setText a public slot of QlineEdit


  • Moderators

    but isn't setText a public slot of QlineEdit

    Yes, a slot that takes a string parameter. The clicked() signal passes no parameters so there's no way to connect these two.
    As I said the SLOT macro does not take parameters from you. It takes it from the signal you connect it to, so they need to match.



  • ok, i think i understand now.

    so, is ther any pushbutton signal that has a qstring parameter, or will o have to make one my self, and then use the diplaytext function to display the text


  • Moderators

    is there any pushbutton signal that has a qstring parameter

    No, buttons don't generate text. They generate clicks.

    So you can either subclass a button and give it a signal that generates text (but that is really messed up conceptually) or simply connect the click to something that doesn't require a parameter (like the lambda example in my previous post).



  • thanks for the reply, really helps



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