A problem that I encountered along the way as I implemented my cache was that any change to the data always caused the array controller to load all the elements. This was exactly what I was trying to avoid with a cache, yet it was happening.

After much hair-pulling (and posting to Apple's Cocoa mailing list) I figured that the array controller believed that my array (implemented by methods in my Random_Wok class) was immutable, and therefore any observed change must mean that the entire array had changed and so need a reload. The fix was to make the array controller believe that the array was mutable. To do this I added three more methods:

These are the mutable array methods. I didn't even have to write any code for them because they are never called. They are just there so that the array controller knows that my array is mutable and so will allow updates to individual elements.

Another problem I found that was while the Page Up and Page Down keys worked on the NSTableView, the Home and End keys did not. A little odd. To fix this I subclassed NSTableView and overrode -keyDown:.

I created a custom class called BTKeydownTableView and told Interface Builder to use it instead of NSTableView. Here is the interface:

The implementation is very simple. I read the first character from the event queue and act on it:

To scroll the window to the right place I tell the view to scroll to the first or last rows, as required.

The other parts of this series can be found via the Cocoa page.

Tags: Aperture, Plug-ins, Caching, Cocoa, Random Wok, NSTableView