glitch in javascript bindings

skylendar

Hi there and thx for reading and answering this post in you can.

I shouldn't ask you that because it worked before but doesn't now. Why ????

I declare 2 C++ classes:

class z: public QObject
{
    Q_OBJECT
 public:
    Q_INVOKABLE z() {}
};

class test: public QObject
{
    Q_OBJECT
 public:
    Q_INVOKABLE test() {}
public slots:
    z* get() { auto x = new z; return x; }
};
`

Then the corresponding declarations for QJSEngine:

QJSValue ZObj = newQMetaObject(&z::staticMetaObject);
 globalObject().setProperty("z", ZObj);
 QJSValue TestObj = newQMetaObject(&test::staticMetaObject);
 globalObject().setProperty("test", TestObj);

so far so good, but when I run a javascript script such as :

var z = new test()
var a = z.get()

QJSEngine returns:

Error: Unknown method return type: z*

What's wrong ?

Thx again for reading this post

Gojir4

@skylendar hi,

Can I ask why are you declaring the constructor of z with Q_INVOKABLE and creating an object in the JS engine ?

QJSValue ZObj = newQMetaObject(&z::staticMetaObject);
 globalObject().setProperty("z", ZObj);

This should not be necessary as you don't need to create the object from Javascript.

Then the function Test::get()must return a Javascript object wrapping instance of z:

QJSValue get() {
    auto x = new z;
    return jsEngine->newQObject(x);
    /* or return jsEngine->newQObject(new z);*/
}

Note that by doing this you avoid memory leak of x because the Javascript engine take ownershipt of the object

Are you sure you want to create a new instance of z each time you call get() from Javascript ? I mean, this is more a create() function :). Or do you want to "share" an object your class Test. Something like that in javascript:

var z = new test()
var a = z.x
z.x.someFunction()

skylendar

Ok, first of, thx for answering.

Q: can I ask why are you declaring the constructor of z with Q_INVOKABLE and creating an object in the JS engine ?
A: I use Q_INVOKABLE because it was suggested in the doc.

Q: Are you sure you want to create a new instance of z each time you call get() from Javascript ?

A: Don't worry, it was just a simple ad-hoc code for this post, not the real code.

but ok, you answered my question with newObject(). I would have preferred something more straightforward.

Thank you again.

Gojir4

@skylendar said in glitch in javascript bindings:

A: I use Q_INVOKABLE because it was suggested in the doc.

Note Q_INVOKABLE is necessary only if you need to call the function from Javascript. In your code sample, this makes constructor of z available from JS, which is seemingly not what you want.

var x = new z()

skylendar

Ooops, I spoke too fast. Actually, nothing works :-(

In my case Q_INVOKABLE is needed. Also, using newQObject() doesn't change anything, since the method and properties aren't available too.

skylendar

This post is deleted!

Gojir4

@skylendar Sorry, I miss your last message.
Any improvements here ?