[Development] QTCS2019 Notes from QtQml session

Ulf Hermann ulf.hermann at qt.io
Wed Nov 27 09:48:28 CET 2019

> Anyway, how would I idiomatically register a bunch of dynamically
> created C++ objects with QML then? As an example, we're automatically
> detecting hardware stuff and creating interface objects based on that.
> These interface objects are then passed to QML which we use to implement
> state machines.

You can have a QJSValue as singleton. There is a 
qmlRegisterSingletonType() that takes a QJSValue factory function. That 
QJSValue can be an object (QJSEngine::newObject()) and the object can 
have arbitrary properties, keyed by strings. Note that you should really 
only do this if you need all the flexibility of creating a completely 
unpredictable "bag of objects". You're deferring all the type checking 
and property resolution to run-time this way.

In QML that would be:

import QtQml.StateMachine 1.0 as DSM
import Utils 0.1  // provides QJSValue singleton "Objects"

DSM.State {
     // just as if "Objects" were a context propery
     onEntered: Objects.foobar.frizzle()


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