On Apr 25, 2014, at 3:51 AM, Alberto Mardegan <ma...@users.sourceforge.net> wrote:
> On 04/24/2014 03:11 PM, Joshua Kolden wrote: > [...] >> We have a solution that works very well for us using QVariantMaps and an >> MVC pattern / strong separation between data objects and view. It >> appears to me that most people are having this issue because it’s not >> common to use MVC with QtWidgets. But you can easily expose complex >> data structures to QtQuick without subclassing QObject via QVariantMaps. > [...] > > While your proposed approach is rather clean, it carries one drawback, > which is the lack of type information, with all its consequences. > > For instance, I would like to have a GeoPoint type with "latitude" and > "longitude" properties; if I exposed it as a QVariantMap, I wouldn't be > able to prevent the QML code from doing stuff like: > p.latitude = 60 > p.longitde = 10 // note the typo > Actually you can (at least at runtime), although we don’t. In the application runtime we use explicit input validation for user input in the view as apposed to relying on compiler errors. This gives us much finer grain control over what constitutes valid data, as apposed to only validating type and existence as compilers do. Also our GUI development is in real time on top of the running application (do that with widgets), so variable typos are immediately obvious. If as I’ve described these data types are QML properties then onChanged is signaled, so you can easily run any type of validator (in javascript or c++). This includes listing all keys in the QVarianMap for `eatra` values that shouldn't be there, missing values, type or range invalidations etc. Also once you grab your data back from the QVariantMap in C++ in the controller you must use an accessor like .toString() etc to cast the QVariant to a known type, and that brings back your type checking on the C++ side. However, what you’ve described is a coding error, as apposed to a user input error, we don’t check this in application code at all nor do we rely on the compiler to catch everything as this is the domain of the test sweet. j > Ciao, > Alberto > > -- > http://blog.mardy.it <- geek in un lingua international! > _______________________________________________ > Development mailing list > Development@qt-project.org > http://lists.qt-project.org/mailman/listinfo/development _______________________________________________ Development mailing list Development@qt-project.org http://lists.qt-project.org/mailman/listinfo/development
