Recent changes to ModelViews

WikiPage ModelViews modified by Martin Herrmann

Martin Herrmann — Sat, 10 Nov 2012 22:38:51 -0000

--- v4
+++ v5
@@ -57,7 +57,7 @@
 
 You may have to reset internal data and/or refresh the view. You can probably use the same methods called on model reset for this.
 
-In a proxy model, the process must be wrapped in calls to `beginResetModel ()` (must be called before resetting internal data) and `endResetModel ()`. You can probably use the methods connected to the source model's signals with the same names.
+In a proxy model, the process of resetting internal data must be wrapped in calls to `beginResetModel ()` and `endResetModel ()`. You can probably use the methods connected to the source model's signals with the same names.
 
 
 ## Reacting to model deletion

WikiPage ModelViews modified by Martin Herrmann

Martin Herrmann — Sat, 10 Nov 2012 22:34:19 -0000

--- v3
+++ v4
@@ -57,7 +57,7 @@
 
 You may have to reset internal data and/or refresh the view. You can probably use the same methods called on model reset for this.
 
-In a proxy model, the process must be wrapped in calls to `beginResetModel ()` (must be called before resetting internal data) and `endResetModel ()`.
+In a proxy model, the process must be wrapped in calls to `beginResetModel ()` (must be called before resetting internal data) and `endResetModel ()`. You can probably use the methods connected to the source model's signals with the same names.
 
 
 ## Reacting to model deletion

WikiPage ModelViews modified by Martin Herrmann

Martin Herrmann — Sat, 10 Nov 2012 22:31:00 -0000

--- v2
+++ v3
@@ -55,7 +55,9 @@
                  this       , SLOT   (modelDestroyed ()));
     }
 
-Refresh the view, if necessary.
+You may have to reset internal data and/or refresh the view. You can probably use the same methods called on model reset for this.
+
+In a proxy model, the process must be wrapped in calls to `beginResetModel ()` (must be called before resetting internal data) and `endResetModel ()`.
 
 
 ## Reacting to model deletion

WikiPage ModelViews modified by Martin Herrmann

Martin Herrmann — Sat, 10 Nov 2012 22:16:14 -0000

--- v1
+++ v2
@@ -27,6 +27,10 @@
     :::C++
     if (this->model)
     {
+        // Disconnect all signals of the model from this view
+        _sourceModel->disconnect (this);
+
+        // Alternatively, you can disconnect the signals individually:
         disconnect (this->model, SIGNAL (dataChanged (QModelIndex, QModelIndex)),
                     this       , SLOT   (dataChanged (QModelIndex, QModelIndex)));
         // ...
@@ -34,7 +38,7 @@
                     this       , SLOT   (modelDestroyed ()));
     }
 
-Store the current model to the new model:
+Store the the new model:
 
     :::C++
     this->model=model;

WikiPage ModelViews modified by Martin Herrmann

Martin Herrmann — Tue, 11 Sep 2012 18:56:15 -0000

Several classes act as model views or something similar. An example for a true model view is `FlarmMapWidget` which is a view for `FlarmList` and `GpsTracker`. An example that is not strictly a model view but uses similar techniques is `GpsTracker` which uses an `NmeaDecoder`. This page describes the techniques employed by these clases. ## General The model may be `NULL`. Make sure that all methods accessing the model handle this case correctly. An alternative technique, used by Qt's own model views, is to use a (static) null object. ## Setting the model The model is set by a method called `setModel` or something more specific (especially for classes using several models) like `setGpsTracker`. This method performes the following steps: Check if the new model is the same as the current model: :::C++ if (model==this->model) return; Disconnect the signals of the old model, if there is an old model: :::C++ if (this->model) { disconnect (this->model, SIGNAL (dataChanged (QModelIndex, QModelIndex)), this , SLOT (dataChanged (QModelIndex, QModelIndex))); // ... disconnect (this->model, SIGNAL (destroyed()), this , SLOT (modelDestroyed ())); } Store the current model to the new model: :::C++ this->model=model; If the new model is valid (it may be NULL), connect its signals. Pay particular attention to the `destroyed()` signal: :::C++ if (this->model) { connect (this->model, SIGNAL (dataChanged (QModelIndex, QModelIndex)), this , SLOT (dataChanged (QModelIndex, QModelIndex))); // ... connect (this->model, SIGNAL (destroyed()), this , SLOT (modelDestroyed ())); } Refresh the view, if necessary. ## Reacting to model deletion In the slot connected to the model's `destroyed()` signal, set the current model to `NULL`: :::C++ this->model=NULL; Do not call `setModel (NULL)` - this will try to disconnect the signals which are no longer valid at this point. You will probably want to refresh the view after that; if the model is a QAbstractItemModel, you can probably use the method connected to the model's `modelReset` slot.