Interception of required properties within c++

magrif

Hi everyone.
I have a c++ class MyClass and declaratively instantiate it in QML like:

MyClass {
    required property int foo
    required property double bar
    required property string baz
}

There is a way to intercept and initialize this properties at c++ side? Q_PROPERTY is not used.

GrecKo

@magrif you can query its metaObject() and list all its properties. QMetaProperty has a isRequired() method.

magrif

I know, but application crashes with error about not initialized required properties before I have call QMetaProperty::write.

GrecKo

How do you instantiate the object?

TomZ

@magrif said in Interception of required properties within c++:

but application crashes with error about not initialized required properties

That has nothing to do with the C++ part.
You wrote "required". Which implies you created a new qml file, right?

Then when someone actually USES that new QML file, they are required to provide those properties.

Like:


Foo.qml
Item {
   required property int foo;
}

Bar.qml
Item {
    Foo {
        foo: 1 // required property is provided here!
    }
}

magrif

@GrecKo said in Interception of required properties within c++:

How do you instantiate the object?

@magrif said in Interception of required properties within c++:

declaratively instantiate it in QML

@TomZ said in Interception of required properties within c++:

Then when someone actually USES that new QML file, they are required to provide those properties.

@magrif said in Interception of required properties within c++:

There is a way to intercept and initialize this properties at c++ side?

magrif

I mean set values somewhere inside MyClass. May be some private interfaces or like QQmlParserStatus.

GrecKo

@magrif Sorry I misiread.

Why do you need the properties to be required?

magrif

@GrecKo No problem. I want make object with shared properties. For instance in one part of application create:

MyClass {
    property int foo: 100
    roperty double bar: 500.0
    property string baz: "Hello"
}

The values of properties will be saved inside a c++-side data structure, details here doesn't matter. And somewhere else initialize them to eponymous properties, if they marked as required:

MyClass {
    required property int foo
    required property double bar
    required property string baz
}

I would be use and without required keyword, just see if property have value or not. And just initialize it by shared value if no have one . But for primitive types (bool, int) its respectivelyQVariant(bool, false)/QVariant(int, 0) rather than QVariant(Invalid) .

So I'm trying figure out how it works inside Qt.