Bug report #15272
QgsVectorLayer's attributeValueChanged SIGNAL emitted when it should not
Status: | Closed | ||
---|---|---|---|
Priority: | Normal | ||
Assignee: | - | ||
Category: | Vectors | ||
Affected QGIS version: | 2.14.2 | Regression?: | No |
Operating System: | GNU/Linux | Easy fix?: | No |
Pull Request or Patch supplied: | No | Resolution: | end of life |
Crashes QGIS or corrupts data: | No | Copied to github as #: | 23208 |
Description
I'm working on a plugin and trying to connect a SLOT to layer.attributeValueChanged SIGNAL. However, I found that such SIGNAL is (weirdly) emitted in the following scenario:
1. Load a vector file (I've tested this with a Shapefile and an SQLITE file) with a numeric (int or real) field, whose value for the first feature is NULL.
2. Open the attribute table of the vector layer.
3. Start an edit session cliking on "Toggle Edit Mode" button from the Attribute table window.
As soon as the edit session starts, the SIGNAL is emitted. Now, if I click on the "Toggle Edit Mode" button from the Attribute table window, I have to choose among Save, Cancel, or Close Without Saving options, even without changing any attribute value at all. Once I choose Close Without Saving, the layer.attributeValueChanged SIGNAL is emitted once more.
######################################
Note: I use this code snippet in the QGIS Python console to be notified when layer.attributeValueChanged is emitted:
##
def f(fid, idx, value):
print fid,idx,value
l = iface.activeLayer()
l.attributeValueChanged.connect( f )
##
I'm getting these messages printed (4 is the index of the numeric field whose value for the first feature is NULL):
0 4 NULL # When I open the edit session.
0 4 NULL # When I close the edit session.
If you want to reproduce the problem, you can use a sample Shapefile from here: http://downloads.tuxfamily.org/tuxgis/tmp/test.zip
######################################
Is this a bug? Do you know why layer.attributeValueChanged is being emitted in such scenario? I've noticed that sometimes a blockSignals() method is used in QGIS source code; couldn't we use blockSignals() to avoid emitting the SIGNAL in this case?
History
#1
Updated by Giovanni Manghi over 7 years ago
- Easy fix? set to No
- Regression? set to No
#2
Updated by Giovanni Manghi over 5 years ago
- Resolution set to end of life
- Status changed from Open to Closed
End of life notice: QGIS 2.18 LTR
Source:
http://blog.qgis.org/2019/03/09/end-of-life-notice-qgis-2-18-ltr/
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