Passing arguments to the QJSEngine

Lolo67

I am trying to pass a list of arguments to a javascript function via the QJSEngine.
The following code will display "The passed amount of arguments is 15" i.e. the length of the first argument passed - looking further I can see that args[0] contains "M", args[1] contains "Y", args[2] contains "F",....,args[15] contains "T" while I was awaiting something like "The passed amount of arguments is 3" where args[0] contains "MYFIRSTARGUMENT", args[1] contains "A", args[2] contains "B".

QJSValueList args;
args << "MYFIRSTARGUMENT";
args << "A";
args << "B";

QJSValue fun = m_jsEngine->evaluate("(function(args) { return args.length; })");
QJSValue result = fun.call(args);
qDebug() << QString("The passed amount of arguments is %1").arg(result.toInt());

JonB

@Lolo67
Where does the documentation actually define QJSValueList? I see it used at http://doc.qt.io/qt-5/qjsvalue.html#call

QJSValue QJSValue::call(const QJSValueList &args = QJSValueList())

but it's not a hyperlink.

SGaist

It's a typedef of QList<QJSValue>

mrjj

Hi
Im have not used this class so this is only a note.
The doc sample seems to have extra parameter to the call function which seems to
relate to your issue that only the first value of the list is used for arg.

Doc sample

QJSValue fun = myEngine.evaluate("(function(a, b) { return a + b; })");
QJSValueList args;
args << 1 << 2;
QJSValue threeAgain = fun.call(QJSValue(), args);

However the call is defined as
QJSValue QJSValue::call(const QJSValueList & args = QJSValueList())

So ~~maybe~~ sample is just wrong.

SGaist

A documentation fix is on its way.

If you remove the QJSValue() from the parameters, the example works as expected.

mrjj

Hi
Ok, rare case of wrong docs :)

So the reason that the OPs code is not working is that he need to specify the parameters separately and
the arg is not/ cannot be used as a list ?
like
m_jsEngine->evaluate("(function(a1,a2, a3) { })");

Lolo67

By the way the same effect can be observed when using QScriptEngine

QScriptEngine *m_ScriptEngine = new QScriptEngine(this);
QScriptValueList scriptArgs;
scriptArgs << "MYFIRSTARGUMENT";
scriptArgs << "A";
scriptArgs << "B";

QScriptValue  fun = m_ScriptEngine->evaluate("(function(args) { return args.length; })");
QScriptValue  result = fun.call(QScriptValue(), scriptArgs);
qDebug() << QString("The passed amount of arguments is %1").arg(result.toInt32());
delete m_ScriptEngine;