How can I set custom text to a QLabel in C++?

Question

I'm working on a C++/Qt simulator which integrates a parameter's page. At the end of the parameters, a QLabel notifies the user whether the entered data is valid or not. This text should appear with a custom color, so I implemented this:

ParametersDialog.h

#include <iostream>
#include <QtWidgets>

using namespace std;

class ParametersDialog: public QDialog {
    Q_OBJECT

    public:
        ParametersDialog(QWidget *parent = nullptr);
        ~ParametersDialog();

    ...

    private:
        QLabel *notificationLabel = new QLabel;
        ...
        void notify(string message, string color);
};

ParametersDialog.cpp

#include "<<src_path>>/ParametersDialog.h"

ParametersDialog::ParametersDialog(QWidget *parent): QDialog(parent) {
    ...
    notify("TEST TEST 1 2 1 2", "green");
}

...

void ParametersDialog::notify(string message, string color = "red") {
    notificationLabel->setText("<font color=" + color + ">" + message + "</font>");
}

I don't understand why it gives me this error:

D:\dev\_MyCode\SM_Streamer\<<src_path>>\ParametersDialog.cpp:65:79: error: no matching function for call to 'QLabel::setText(std::__cxx11::basic_string<char>)'
  notificationLabel->setText("<font color=" + color + ">" + message + "</font>");
                                                                               ^

I understand that my string concatenation has created a basic_string<char> element that cannot be set as a QLabel text.

What could be the simplest implementation of my notify method?

a `basic_string` is just `std::string` but the method takes a `QString` — 463035818_is_not_an_ai, May 26 '20 at 08:56
I've tried this solution but it gives me a similar error: `notificationLabel->setText(QString("" + message + ""));` — 0009laH, May 26 '20 at 08:58
Does this answer your question? https://stackoverflow.com/questions/1814189/how-to-change-string-into-qstring — 463035818_is_not_an_ai, May 26 '20 at 09:09
Yes it works, I forgot that `QString` cannot be built like I did :) Thank you very much — 0009laH, May 26 '20 at 09:46

score 2 · Accepted Answer · answered May 26 '20 at 09:16

2

the problem is that std::string and QString are not straight forward concatenable...

a trick can be done:

QString mx = "<font color=%1>%2</font>";
notificationLabel->setText(mx.arg(color.c_str(), message.c_str()));

answered May 26 '20 at 09:16

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How can I set custom text to a QLabel in C++?

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