gistfile1.m

- (void)keyDown:(CPEvent)anEvent
{
    var keyCode = [anEvent keyCode];

    var index = [[_documentsOutlineView selectionIndexes] firstIndex],
        count = [[_documentsOutlineView content] count];
    
    switch(keyCode)
    {
        case 37: //left
        case 38: //up
                 [_documentsOutlineView setSelectionIndexes:[CPIndexSet indexSetWithIndex:MAX(index-1, 0)]];
                 break;
                                 
        case 39: //right
        case 40: //down
                 [_documentsOutlineView setSelectionIndexes:[CPIndexSet indexSetWithIndex:MIN(index+1, count-1)]];
                 break;
                 
        default: [super keyDown:anEvent];                
    }
}