[Interest] QJSEngine replacement for QScriptEngine misses newFunction

[nikita baryshnikov]

As a workaround you can use QQmlContext::setContextObject:

QQmlEngine::rootContext()->setContextObject(myMath);

On Tue, Feb 23, 2016 at 2:11 PM, Stephen Bryant <steve at bawue.de> wrote:
> Hi Stefan,
>
> On Tuesday 23 February 2016 05:34:03 Walter Stefan wrote:
> [...]
>>
>> And in this way. I can use it then in the script:
>> value = sqrt(4);
>>
>> I actually don't want to map a whole QObject, because that would require a
>> call like this: value = MyMath.sqrt(4);
>>
>> Is there any way to achive in QJSEngine the same result as I do within the
>> QScriptEngine?
>
>
> Is far as I know, the only way is to do the thing you don't want to: map the
> whole QObject.  You can, however, add a JS function reference inside the
> engine so you can call the function without the object name.
>
> QJSEngine engine;
> engine.globalObject().setProperty(
>   "MyMath",
>   engine.newQObject( new ScriptModuleMath( &engine ) )
> );
> engine.evaluate( "var sqrt=MyMath.sqrt;" );  // repeat for other functions
>
> This will now work in JS:  value = sqrt(4);
>
> You'll presumably be aware that all public slots of MyMath will automatically
> be available as JS functions.  That makes things a little easier.
>
> It seems that you also need a QObject instance, event if you only want to
> expose static methods.
>
> BTW: your C++ native function can use this signature: double sqrt(double);
> You'll get NaN if somebody calls it with a non-number.  The return value is
> also automatically converted as there is a QJSValue constructor that takes a
> double.
>
>
> There's no direct equivalent of read-only/undeletable, unfortunately.  I'm
> missing that too.  The closest you can get is that your MyMath functions can't
> be altered from JS, and you can also make a read-only Q_PROPERTY.
>
> However, there is nothing stopping somebody from reassigning properties of the
> global object - so your 'sqrt' function and 'MyMath' object could be replaced.
> This may be a security concern, depending on what you're doing.
>
>
> Best regards,
>
> Steve
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