Hi All I would like to still get back to the goal of this exercise. From the discussion I see at least a couple of conceptually different reasons for "+=".
1) Just accumulation (add one more log line) 2) Make parent care about one more child (one more rectangle to represent one more file in the file system) 3) Modify the default set of elements (get a list of files from file system and add one "pseudo-file item" for the current dir or mix lists of files from two dirs). IMHO, all of these reasons are best to be solved by the different means, non of which seems to require "+=" to me. 1) Just accumulation (add one more log line) Well, then it's just a Javascript function addLogLine() that might modify declarative lists or models if it likes to store log in the declarative structures 2) Make parent care about one more child (one more rectangle to represent one more file in the file system) That is more about making the UI follow a dynamically changing model. Model can come from C++ or be a QML ListModel. In both cases there are already enough facilities to modify he models, UI should follow 3) 3) Modify the default set of elements (get a list of files from file system and add one "pseudo-file item" for the current dir or mix lists of files from two dirs). This one is a little more complex and looks to me similar to relational algebra where you may like to combine models, intersect them, add pseudo-elements, remove/hide some elements (e.g. hidden files). On a C++ side Qt's proxy models can help you to some extent, on JavaScript it takes some more manual work. I had a similar issue lately, a contact list of the instant messenger coming as a C++ model needed some modification: a couple of contacts need to be hidden, one pseudo-contact is to be added. What I did was a secondary model in QML (ListModel) that was recreated/adjusted on every source model modification. OnDataChanged handlers were acting almost as predicates transforming the source model into a model good for a final UI. Now that, certainly, diverts the topic a little. The point I am trying to make is that I don't see so far a single clear reason for += syntax not achievable with the current QML/JS mechanisms. Cheers, Artem. -- Artem Marchenko Sent with Sparrow (http://www.sparrowmailapp.com/?sig) On Wednesday, 2 May 2012 р. at 11:22, Sven Anderson wrote: > On 01.05.2012 13:58, Charley Bay wrote: > > Bo Thorsen respondeth: > > += doesn't make any sense here. It's for the javascript code only. > > > > > You can also just say: += creates an invalid loop binding. And we all > accept, that loop bindings cannot work. > > > Item { > > some_val: parent.some_val; // binding to parent > > some_val2: 10; // assign value (not bind) > > > > > I don't agree. Semantically this is a normal binding to a constant > value. That some binding overhead is avoided in this case, because there > will never be an update, is an implementation detail, that isn't > important to the QML developer. > > > BR > > Sven > > _______________________________________________ > Qt-qml mailing list > Qt-qml@qt.nokia.com (mailto:Qt-qml@qt.nokia.com) > http://lists.qt.nokia.com/mailman/listinfo/qt-qml > >
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