QtScript : passing array as argument into function

Greetings,

I've been playing around with the newer QtScript functionality from Qt 4.3, and right now I'm trying to figure out the best way to allow me to modify a QByteArray in a script function.

Preferrably it would be something treated as a normal script Array (so you can use the [] to access elements).

By subclassing QByteArray and adding Q_OBJECT, I've been able to get a class that I can use QScriptEngine::newQObject() with, and pass as a QScriptValue into the script function (to which I can access the methods designated as 'slots').

From some testing it would appear that I cannot make 'operator[]' a slot (compiler gives an error 'Not a signal or slot declaration'); so my question is, is there a way to achieve a normal array functionality through a passed-in QByteArray (or some derivative thereof)?

Any ideas/insight would be appreciated!

Thanks,
Derek R.

You can provide get/set methods for the class.

Quote:

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Originally Posted by wysota

You can provide get/set methods for the class.

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Sorry I should have given a bit more detail, I currently have get/set methods to allow me to get/set elements in the QByteArray however I was trying to find a way to provide 'operator[]' functionality in the script.

Currently I have this:

Code:

---

function test(arg) {
    print("arg[0] = " + arg.getAt(0) + "\n");
    arg.setAt(0,123);
}

---

What I'm trying to achieve is this:

Code:

---

function test(arg) {
    print("arg[0] = " + arg[0] + "\n");
    arg[0] = 123;
}

---

Is the latter possible with QtScript?


Derek R.

I still haven't been able to find a solution to the operator[] question so I've just been doing tests using my set/get methods for array access.

The problem I'm running into now is the speed of accessing the array, just a relatively small array size of 100000 entries takes ~3s to iterate through and set.

I was expecting maybe a few orders of magnitude difference in speed (versus normal C++ execution), however this is more like several orders of magnitude difference. Is there any way to speed this up, or a different way to pass in and modify a byte array in a script function?

Derek R.

Are there any news concerning your approach?

If you only want to use the operator[], something like this may help:

Code:

---

QScriptEngine *engine = new QScriptEngine();
QByteArray byteArray;
 
QScriptValue array = engine->newArray(byteArray.size())
for (int i = 0; i < byteArray.size(); ++i)
    array.setProperty(i, QScriptValue(engine, byteArray[i]);

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The QScriptValue can then be handed over to the engine. However, the drawbacks of this approach are that you have to hard-copy the whole QByteArray and that it will not work with your subclass-method (at least I cannot see how :) ).

To copy the QScriptValue back to the QByteArray, try something like this:

Code:

---

QByteArray byteArray;
uint len = array.property("length").toUInt32();
byteArray.resize(len);
for (uint i = 0; i < len; ++i)
    byteArray[i] = values.property(i).toInt32());

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I hope this helps, lucky coding :)