[Interest] What is beginInsertRows() purpose?

[Paul Miller]

On 8/23/2013 9:08 AM, Etienne Sandré-Chardonnal wrote:
> But... I always wondered why it is necessary to have both signals (one
> before and one after) in the underlying mechanism, and what could be
> wrong in doing:
>
> -modify the model underlying data structure by inserting rows-
> beginInsertRows()
> endInsertRows()
>
> Instead of the regular:
> beginInsertRows()
> -modify the model underlying data structure by inserting rows-
> endInsertRows()
>
> It's always better to understand why are things done how they are...

begin/endInsertRows/Columns tells the view that you are about to change 
the model. Views can then "wait" to refresh or build their internal data 
structures until the rows/columns have been inserted in the model. Since 
view updates could be expensive, this is a useful optimization.

If you're doing a lot of complex model updates, such as 
inserting/deleting lots of rows you could always just call modelReset(), 
but depending on the view that may cause the view to scroll back to the top.