How qml call static method from c++ - c++11

Question

What I done:
validator.h:
class UTILSSHARED_EXPORT Validator: public QObject {
Q_OBJECT
public:
Validator(QObject *parent = 0);
~Validator();
Q_INVOKABLE static bool validateMobile(const QString target);
};
main.cpp:
qmlRegisterUncreatableType<Validator>("CT.Utils", 1, 0, "ValidatorKit", "It just a kit");
qml:
import CT.Utils 1.0
ValidatorKit.validateMobile("112344")
But unfortunately, I got an error that said: TypeError: Property 'validateMobile' of object [object Object] is not a function
So, how can I expose static method to qml correctly?
Could anybody help me? Thanks a lot.

Answer 1

qmlRegisterUncreatableType() is about something else entirely.
What you actually need to do is expose a Validator instance as a context property to QML, or even better, implement the validator as a singleton.
qmlRegisterSingletonType<Validator>("CT.Utils", 1, 0, "ValidatorKit", fooThatReturnsValidatorPtr);

Answer 2

Addition to singleton type, it is possible to create a private singleton attached properties object which contains only static functions. It is more clear with an example:
class StaticValidator;
class Validator : public QObject {
Q_OBJECT
public:
Validator(QObject *parent = 0);
~Validator();
// Put implementation in a source file to prevent compile errors.
static StaticValidator* qmlAttachedProperties(QObject *object) {
Q_UNUSED(object);
static StaticValidator instance;
return &instance;
}
static bool validateMobile(const QString& target);
};
//Q_OBJECT does not work in inner classes.
class StaticValidator : public QObject {
Q_OBJECT
public:
Q_INVOKABLE inline bool validateMobile(const QString& target) const {
return Validator::validateMobile(target);
}
private:
StaticValidator(QObject* parent = nullptr) : QObject(parent) {}
friend class Validator;
};
QML_DECLARE_TYPE(Validator)
QML_DECLARE_TYPEINFO(Validator, QML_HAS_ATTACHED_PROPERTIES)
Register type in main or somewhere:
qmlRegisterType<Validator>("Validator", 1, 0, "Validator");
Call function in QML:
import Validator 1.0
...
var result = Validator.validateMobile(target);
It should also work in Qt4, but I didn't test it.