NSClassFromString equivalent for BlackBerry-10

Question

Does NSClassFromString from iOS have an equivalent in the BlackBerry 10 SDK?

C++ is not a language that uses a runtime, so it has no equivalent. — borrrden, Feb 05 '13 at 15:07
There are very few cases when you really need this method. Probably you should redesign the app to avoid this method at all. — Sulthan, Feb 05 '13 at 17:04
Voting to reopen - Just because the answer is 'no' doesn't make this less of a question. — Michael Donohue, Feb 05 '13 at 18:00

score 0 · Answer 1 · edited May 23 '17 at 10:24

You cannot do this natively in C++, C++ is a fairly static language that does not have the runtime capabilities that Objective-C has. It is possible, with a bit of hard graft, if you map all your Class names with instances, using the template mechanism. This is described in "Is there a way to instantiate objects from a string holding their class name? ".

As for the BB10 SDK, based on the assumption that it's Java, this is possible.

Class myClassName = Class.forName("ClassName");
ClassName myInstance = myClassName.newInstance();

Update: BB10 SDK is C++, as such there isn't a native way to do this, except what is mentioned above.

BB10 is actually C++ based. It can run Android applications but its native language is C++. — Sulthan, Feb 05 '13 at 17:02

score 0 · Accepted Answer · answered Feb 09 '13 at 12:47

Yes, there is an equivalent to NSClassFromString provided you use the Qt meta type system.

You'll need to use to Q_DECLARE_METATYPE macro and qRegisterMetaType:

class UserClass : public Superclass {
    ...
}

Q_DECLARE_METATYPE(UserClass)


int main(int argc, char *argv[]) {
    qRegisterMetaType<UserClass>("UserClass");

    ....
}

Then you can create an instance of your class with the following code:

int id = QMetaType::type("UserClass");
UserClass *instance = (UserClass*)(QMetaType::construct(id));

I guess this approach to create objects is used by QML as well, e.g. in the attachedObjects section.

NSClassFromString equivalent for BlackBerry-10

2 Answers2