[Qgis-user] QgsVectorFileWriter

[Borys Jurgiel]

> > > In this way, it would be better to save in a temporary shapefile first,
> > > and if the process finishes successfully, remove the destination
> > > shapefile and copy the temporary shp to the new location.
> > >   
> > hmm, I don't  know about this...
> > Firstly, it's only useful to do this if you're concerned about the 
> > initial file, but since you appear to be writing to a tmp directory, 
> > this probably isn't all that critical...
> Sometimes I don't want to get 2 versions of a shp and select the source
> shp to be overwritten. If something goes wrong and the source is deleted
> first, all is lost...

I've implemented something very similar in the recent Table Manager:
  1. save the modified layer to the temp directory
  2. try to remove an old dbf~ backup if any (see the next point)
  3. backup the original dbf file as dbf~
  4. replace the original dbf with that one from the temp.

You can see it in the tableManager_gui.py file, method TableManager.doSave 
(today they are lines 441-508)