UITableView :cellForRowAtIndexPath Continues being called

Question

I have a UITableView Controller and a UITableView. I have everything set up using the delegates etc, and it populates fine. I notice a small bug however with the following method:

:cellForRowAtIndexPath

I am noticing that this method is continually called every time I scroll the table. Even after the table is populated, it continues to call. Basically, a cell moves out of view, when it comes back in view, it is calling it again. I had NSLog print out the cell contents within that method, which is how I know it continues to call.

Should that function not just call once per cell, to populate it, then be done?

Answer 1

Nope. That's called every time a cell is needed, and a cell is needed every time one is rendered.

UITableView is a very clever little critter. It literally keeps only the cells it's displaying, plus a cache of literally two or three more. When the time comes to scroll a cell on that wasn't on, it can be asked for a cell from the cache, and if there is one, it gets reused.

This way HUGE data sets can be displayed in a UITableView, because there really aren't a large number of cells in memory, only the ones on the screen and a small cache.

Answer 2

This is correct behavior. It has to do with the dequeueing of UITableViewCells. That is why cell reuse is important. This way there are ideally a finite, small amount built in memory that continually get reused.

Check out the docs for more info and code samples.