c++ - 在 QT5 中将信号连接到 c++11 lambda

Question

我尝试将 QDoubleSpinBox 信号连接到 c++11 lamda:

QObject::connect(sbox_roughness, &QDoubleSpinBox::valueChanged,
               [=]() { std::cout << "value changed" << std::endl; });

这给了我:

error: no matching function for call to ‘Game::connect(QDoubleSpinBox*&, <unresolved overloaded function type>, Game::initGui()::<lambda()>)’
                [=]() { std::cout << "value changed" << std::endl; });
note:   no known conversion for argument 2 from ‘<unresolved overloaded function type>’ to ‘const char*’

我试过了 this :

QObject::connect(sbox_roughness, static_cast<void (QDoubleSpinBox::*)(int)>(
                                   &QDoubleSpinBox::valueChanged),
               [=]() { std::cout << "value changed" << std::endl; }); 

给我:

error: no matches converting function ‘valueChanged’ to type ‘void (class QDoubleSpinBox::*)(int)’
                                    &QDoubleSpinBox::valueChanged),

我在这里错过了什么？

Answer 1

QDoubleSpinBox spinbox;

QObject::connect(&spinbox, &QDoubleSpinBox::valueChanged,
                 []() { qDebug() << "value changed"; });

这会失败，因为 QDoubleSpinBox 有两个 valueChanged 信号，您无法在此处决定要连接到哪一个。

QObject::connect(&spinbox, static_cast<void (QDoubleSpinBox::*)(int)>(
                                  &QDoubleSpinBox::valueChanged),
                []() {  qDebug() << "value changed"; });

这失败了，因为 QDoubleSpinBox 没有 valueChanged(int) 信号。

这会起作用:

QObject::connect(&spinbox, static_cast<void (QDoubleSpinBox::*)(double)>(
                                  &QDoubleSpinBox::valueChanged),
                []() {  qDebug() << "value changed"; });

QObject::connect(&spinbox, static_cast<void (QDoubleSpinBox::*)(const QString &)>(
                                  &QDoubleSpinBox::valueChanged),
                []() {  qDebug() << "value changed"; });