[Qt-qml] enumerations in QML

[Gregory Schlomoff]

Isn't there a way to expose an enum to QML with qRegisterType or something?

How do you guys expose enumerations to QML?

While I understand that Javascript is weakly typed and hasn't such
concept as constants, when you are developing generic components, it's
very scary to do stuff like that:

MyScrollbar {
  orientation: "vertical"
}

You just know that one day someone is going to mispell "vertical" or
"horizontal", and the guy is going to have a hard time debugging the
issue.

In this case, I worked around the problem by reusing a Qt global enum,
but that doesn't always work:

MyScrollbar {
  orientation: Qt.Vertical  //much better :)
}



On Thu, Aug 5, 2010 at 11:11 AM, Alan Alpert <alan.alpert at nokia.com> wrote:
> On Thu, 5 Aug 2010 10:36:29 ext Alex wrote:
>> Is there any way to declare enumerations in QML?  For example, assume I
>> have a custom element called "MyText" that has a property called
>> sizeType, for which the possible values are: "small", "medium", or
>> "big."
>>
>> The implementation of MyText will set the correct point or pixel size
>> based on the value of sizeType.  Is there a way to expose the possible
>> values using an enum (e.g., MyText::SizeBig) rather than something
>> more primitive like int or string?
>
> Not from QML. From what I understand, since Javascript is a weakly typed
> language anyways, the appropriate Javascript way is to just use a string
> (which has valid values of "small", "medium" and "large", and a specified
> behavior for invalid values).
>
>> Similarly, what is the best way to declare constants?
>
> Again my understanding of Javascript suggests that you create constants by
> having variables that you ask people not to set. Same for when using
> Javascript in QML.
>
> These concepts make more sense in a statically typed language like C++ than in
> a dynamically typed language like Javascript. So, while it's acceptable to let
> the terms leak in from C++ due to the tight C++ integration in QML, I don't
> think you should worry about them too much when writing pure QML. If you want
> very concrete elements, perhaps you should write them in C++.
>
> --
> Alan Alpert
> Software Engineer
> Nokia, Qt Development Frameworks
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