我想知道是否有人知道交易是什么:是否使用了信号参数?
这是一种检查方法:
#include <QApplication>
#include <QQmlApplicationEngine>
#include <QDebug>
class MyType : public QObject
{
Q_OBJECT
Q_PROPERTY(bool foo READ foo WRITE setFoo NOTIFY fooChanged)
public:
MyType(QObject *parent = nullptr) :
QObject(parent),
mFoo(0)
{
}
bool foo() const
{
qDebug() << Q_FUNC_INFO;
return mFoo;
}
void setFoo(bool foo)
{
if (foo == mFoo)
return;
mFoo = foo;
emit fooChanged(mFoo);
}
signals:
void fooChanged(bool foo);
private:
bool mFoo;
};
int main(int argc, char *argv[])
{
QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
QApplication app(argc, argv);
qmlRegisterType<MyType>("App", 1, 0, "MyType");
QQmlApplicationEngine engine;
engine.load(QUrl(QLatin1String("qrc:/main.qml")));
return app.exec();
}
#include "main.moc"
主要.qml:
import QtQuick 2.0
import QtQuick.Window 2.0
import QtQuick.Controls 2.0
import App 1.0
Window {
width: 400
height: 400
visible: true
Switch {
id: fooSwitch
}
MyType {
id: myType
foo: fooSwitch.checked
onFooChanged: print("onFooChanged, foo =", foo)
// onFooChanged: print("onFooChanged myType.foo =", myType.foo)
}
}
来回切换时的输出为:
qml: onFooChanged, foo = true
qml: onFooChanged, foo = false
因此可以肯定地说,使用了该值而不是 getter。
要查看未使用信号参数时的输出情况,请取消注释行并注释掉另一行:
bool __cdecl MyType::foo(void) const
qml: onFooChanged myType.foo = true
bool __cdecl MyType::foo(void) const
qml: onFooChanged myType.foo = false