Qt-interest Archive, February 2008
QtScript - creating/passing QObject classes from within script
Message 1 in thread
Here's another hopefully simple question. The documentation is a bit
erratic on this topic. What I'm looking at doing is using QtScript to
"set up" my object model when my app starts up, as a method of rapid
prototyping.
I want to expose some QObject-derived classes to the scripting system,
so I can do something like this:
var mo = new MyObject();
globalObject.addMyObject(mo);
I've got the first line working, with this bit of code:
static QScriptValue myObject_construct(QScriptContext *ctx,
QScriptEngine *engine)
{
return engine->newQObject(
new MyObject(),
QScriptEngine::AutoOwnership);
}
QScriptValue moType = engine.newQMetaObject(&MyObject::staticMetaObject,
engine.newFunction(myObject_construct, 0));
engine.globalObject().setProperty(
"MyObject",
engine.newQMetaObject(&MyObject::staticMetaObject,
engine.newFunction(myObject_construct, 0)));
Now, I've exposed my "global" object (globalObject) with this piece of code:
GlobalObject go;
engine.globalObject().setProperty(
"globalObject",
engine.newQObject(&go));
But, in the script, when I call addMyObject(), I get this exception:
uncaught exception at line -1: TypeError: cannot call addMyObject():
unknown type `MyObject*'
What did I miss?
--
[ signature omitted ]
Message 2 in thread
Paul Miller wrote:
> Here's another hopefully simple question. The documentation is a bit
> erratic on this topic. What I'm looking at doing is using QtScript to
> "set up" my object model when my app starts up, as a method of rapid
> prototyping.
>
> I want to expose some QObject-derived classes to the scripting system,
> so I can do something like this:
>
> var mo = new MyObject();
> globalObject.addMyObject(mo);
[...]
> But, in the script, when I call addMyObject(), I get this exception:
>
> uncaught exception at line -1: TypeError: cannot call addMyObject():
> unknown type `MyObject*'
>
>
>
> What did I miss?
>
Hi Paul,
MyObject* is not a built-in type, so QtScript doesn't know how to
convert a script value to that type. The easiest solution is to change
your GlobalObject::addMyObject() function to take a QObject* argument
instead, or QWidget* if your objects are widgets (these are both
built-in types). If necessary, you can use qobject_cast to do
type-checking in your function. The alternative solution is to install
your own conversion functions for MyObject* with qScriptRegisterMetaType().
Regards,
Kent
--
[ signature omitted ]
Message 3 in thread
Kent Hansen wrote:
> Paul Miller wrote:
>
>> But, in the script, when I call addMyObject(), I get this exception:
>>
>> uncaught exception at line -1: TypeError: cannot call addMyObject():
>> unknown type `MyObject*'
>>
>>
>>
>> What did I miss?
>>
>>
>
>
> Hi Paul,
> MyObject* is not a built-in type, so QtScript doesn't know how to
> convert a script value to that type. The easiest solution is to change
> your GlobalObject::addMyObject() function to take a QObject* argument
> instead, or QWidget* if your objects are widgets (these are both
> built-in types). If necessary, you can use qobject_cast to do
> type-checking in your function. The alternative solution is to install
> your own conversion functions for MyObject* with qScriptRegisterMetaType().
>
Actually there's a better alternative in this particular case; you just
have to make MyObject* known to the meta-type system.
Q_DECLARE_METATYPE(MyObject*)
...
qMetaTypeId<MyObject*>();
Then it should "just work" with the rest of your code as-is. We'll try
to improve the docs on this subject.
Regards,
Kent
--
[ signature omitted ]
Message 4 in thread
Kent Hansen wrote:
>> MyObject* is not a built-in type, so QtScript doesn't know how to
>> convert a script value to that type. The easiest solution is to change
>> your GlobalObject::addMyObject() function to take a QObject* argument
>> instead, or QWidget* if your objects are widgets (these are both
>> built-in types). If necessary, you can use qobject_cast to do
>> type-checking in your function. The alternative solution is to install
>> your own conversion functions for MyObject* with qScriptRegisterMetaType().
>>
>
> Actually there's a better alternative in this particular case; you just
> have to make MyObject* known to the meta-type system.
>
>
> Q_DECLARE_METATYPE(MyObject*)
> ...
> qMetaTypeId<MyObject*>();
>
> Then it should "just work" with the rest of your code as-is. We'll try
> to improve the docs on this subject.
It does! I'm curious why making my subclass a Q_OBJECT doesn't
automatically do this for me.
--
[ signature omitted ]
Message 5 in thread
Paul Miller wrote:
> Kent Hansen wrote:
>> Actually there's a better alternative in this particular case; you just
>> have to make MyObject* known to the meta-type system.
>>
>>
>> Q_DECLARE_METATYPE(MyObject*)
>> ...
>> qMetaTypeId<MyObject*>();
>>
>> Then it should "just work" with the rest of your code as-is. We'll try
>> to improve the docs on this subject.
>
> It does! I'm curious why making my subclass a Q_OBJECT doesn't
> automatically do this for me.
>
>
Indeed, it's possible to make this work without the hassle. I've created
a task for this issue, you can track it at
http://trolltech.com/developer/task-tracker/index_html?id=200599&method=entry
(the link won't go "live" for a few hours yet).
Regards,
Kent
--
[ signature omitted ]
