Why are upper-cased properties not supported in QML?

mwallnoefer

What is the reason that Qt properties need to begin with a lower-cased letter in order to be exposed to QML?

Example: this works

C++

class Model : public QAbstractListModel
{
...
    Q_PROPERTY(int name READ name WRITE setName NOTIFY nameChanged)
    Q_PROPERTY(int age READ age WRITE setAge NOTIFY ageChanged)
...
};

QML:

Person {
   name: "Otto"
   age: 30
...
}

This not (odd error message in the QML code at runtime):

class Model : public QAbstractListModel
{
...
    Q_PROPERTY(int Name READ name WRITE setName NOTIFY nameChanged)
    Q_PROPERTY(int Age READ age WRITE setAge NOTIFY ageChanged)
...
};

QML:

Person {
   Name: "Otto"
   Age: 30
...
}

raven-worx

@mwallnoefer
because there are default created changed-slots for each property following the pattern on<CamelCasePropertyName>Changed() (if NOTIFY was specified)

mwallnoefer

Okay, but it seems that also the following piece does not work or am I missing something? Also when omitting the NOTIFY clause I get always the same "Invalid attached object assignment" error.

class Model : public QAbstractListModel
{
...
    Q_PROPERTY(int Name READ Name WRITE setName NOTIFY NameChanged)
    Q_PROPERTY(int Age READ Age WRITE setAge NOTIFY AgeChanged)
...
};

For me this seems more like a bug, since in C++ code upper cased properties are perfectly valid. Alternatively, the docs could be updated to contain an explicit reference to this restriction of QML (for instance in the section about Q_PROPERTY):

Julien B

Hello @mwallnoefer,

The documentation currently refers to this in property attributes

mwallnoefer

@Julien-B Okay, but then it should go also in the Q_PROPERTY section.

But the interesting thing is, that person.Name or person.Age does work though. Only the class assignment syntax with the colon does not.

Thomas Hartmann

Capital letter properties are reserved for so called attached properties (http://doc.qt.io/qt-5/qtqml-syntax-objectattributes.html).