Qt c ++ connect signal with non-void signature to lambda
I want to connect a signal with a non-void signature to a lambda function. My code looks like this
QTimeLine *a = new QTimeLine(DURATION, this);
connect(a, &QTimeLine::valueChanged, [a,this](qreal r) mutable { this->setMaximumHeight(r);});
in a way similar to the SIGNAL-SLOT approach:
connect(a, SIGNAL(valueChanged(qreal),this,SLOT(doStuff(qreal)));
My connect-to-lambda compiles, but it doesn't change this->height()
. What am I wrong? How to write a lambda so that it is qreal
from valueChanged
? I've read the related documentation but haven't found any useful examples.
**** **** EDIT
It actually works, I used the QTimeLine settings incorrectly. And yes, I don't need to capture a
. I am trying to animate a native insertRow()
QTableWidget method . I also made a lambda to change the row height of the table, not the containing widget. For reference, here's a working snippet:
QTimeLine *a = new QTimeLine(DURATION,this);
connect(a,&QTimeLine::valueChanged,[this](qreal r) mutable {
this->list->setRowHeight(0,r * ROW::HEIGHT);
});
a->start();
Anyway, thanks for the quick answers.
source to share
It should just work. Here is a complete SSCCE that demonstrates that it works. Check what you do differently in the principles.
main.cpp
#include <QTimeLine>
#include <QObject>
#include <QDebug>
#include <QCoreApplication>
class Foo
{
void setMaximumHeight(int h) {height = h; qDebug() << "Height:" << height;}
public:
void doStuff() { QObject::connect(&timeLine, &QTimeLine::valueChanged, [this](qreal r) mutable { setMaximumHeight(r);}); timeLine.start(); }
int maximumHeight() const { return height; }
int height{0};
int DURATION{100};
QTimeLine timeLine{DURATION};
};
int main(int argc, char **argv)
{
QCoreApplication application(argc, argv);
Foo foo;
foo.doStuff();
return application.exec();
}
main.pro
TEMPLATE = app TARGET = main QT = core CONFIG += c++11 SOURCES += main.cpp
Build and run
qmake && make && ./main
source to share