PyQt QtWebKit - Return value from a Python method directly to JavaScript

Question

EDIT:

I've found a solution here: how do I correctly return values from pyqt to JavaScript?

I'll post the code first:

Python code:

class JSBridge(QObject):
    def __init__(self, parent=None):
        super(JSBridge, self).__init__(parent)

    @pyqtSlot(bool)
    def fromJStoPython(self, param):
        print param
        print param.toBool()
    @pyqtSlot()
    def returnValue()
        return "hello world"

class another():
    ...
    view = QWebView()
    frame = view.page().mainFrame()

    param = "blabla"
    frame.evaluateJavaScript("printIt('" + param + "');")
    paramBool = True
    frame.evaluateJavaScript("fromPythonWithParameterBool('" + paramBool + "');")

JavaScript:

function printIt(param)
{
    alert(param);
}
function toPython()
{
    jsBridgeInst.fromJStoPython(true);
}
// now here functions I've questions about:
function fromPythonWithParameterBool(param)
{
    alert(param);
}
function fromPythonReturnValue()
{
    res = jsBridgeInst.returnValue();
    alert(res);
}

Now to my question:

The printIt function works fine. So the param is interpreted as a String. The fromJStoPython function also works fine. The print statement shows it's a QVariant.

But the fromPythonWithParameterBool function does not work, because I have to convert paramBool into a string in order to connect it. If I do so, it's printing the string value (but I want it to be boolean). Is it possible to pass a boolean, so that in JavaScript I can work with it as a boolean? If yes, how do you do it?

And for the fromPythonReturnValue function, it does not show an error, but res is undefined. Why? I was searching for that problem, but mostly the examples/tutorials show standard stuff like:

evaluateJavaScript("alert('9')";)

I've worked with Java and SWT, and there I could just simply return a value (as in the formPythonReturnValue method). There was a Browser class where you could implement your methods to call, just like JSBridge.

Answer 1

The fromPythonWithParameterBool doesn't work because you are not generating an input string that can be evaluated as javascript.

What you need to do is something like this:

>>> script = 'fromPythonWithParameterBool(%s);' % str(bool(paramBool)).lower()
>>> print(script)
fromPythonWithParameterBool(true);

So the resulting string is now a fragment of valid javascript.

The problem with fromPythonReturnValue (as you already seem to have discovered), is that you are not specifying the type of the return value. This has to be done explicitly, using the pyqtSlot decorator:

    @pyqtSlot(result=str)
    def returnValue(self):
        return 'hello world'