qt - How to get Javascript in a QWebView to create new instances of C++ based classes?

Question

I've successfully added an C++ object to a QWebFrame with addToJavaScriptWindowObject, and can call a slot on that object from javascript.

But what I really want to do is have one of those slots return a new object. For example, I have a slot like this, which returns a QObject derived class instance:

   MyObject* MyApp::helloWorld()
   {
          //MyObject is dervied from QObject
          return new MyObject();
   }

I can call this slot from javascript successfully like this

   var foo=myapp.helloWorld();

But foo appears to be empty, I can't call any slots or access any properties on it from Javascript.

Any ideas on how I can achieve this?

Answer 1

One rather ugly hack I've considered is to use addToJavaScriptWindowObject to drop the object I want to return into the window object with a random name, then have my slot return the name of the object instance instead:

QString MyApp::helloWorld()
{
     //general a unique name for the js variable
     QString name=getRandomVariableName();

     //here's the object we want to expose to js
     MyObject* pReturn=new MyObject();

     //we make attach our object to the js window object    
     getWebFrame()->addToJavaScriptWindowObject(name, pReturn,
         QScriptEngine::ScriptOwnership);  

     //tell js the name we used
     return name;
}

The JS can be written to check if the return value is a string, and if it is, grab the object from the window.:

var foo=myapp.helloWorld();
if (typeof foo == "string")
{
    foo=window[foo];
}

A little ugly, but will get me by until a better method comes along. Future Qt versions are going unify the scripting support so that it's all based on the JavaScriptCore in WebKit, so hopefully this will improve then!