iOS-将单元格添加到带有核心数据和NSFetchedResultsController的空UITableView部分

Question

I'm using Core Data and an NSFetchedResults controller to populate a UITableViewCell (plain style) in my app. The TableView has 3 sections, each with a viewForHeaderInSection and a viewForFooterInSection. The user will be entering items that will be put in each section.

When one of the sections has no items in it, it completely disappears. I'm wondering if it would be possible to make it so if a section is empty, it would display a new cell that would say "no entries" or something like that (maybe with a UIImageView or another view?), which would then go away if a new item was put into that section.

Does anyone know how to accomplish this?

Here's the code for my data source.

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return [[self.fetchedResultsController sections] count];
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{    
   return [[[self.fetchedResultsController sections] objectAtIndex:section] numberOfObjects];
}

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
{
    return [[[self.fetchedResultsController sections] objectAtIndex:section] name];
}

Also, the section itself gets removed from the TableView when it has no rows, so how could I make it so the "no entries" cell gets added to the correct section?

Answer 1

If the section don't appear in the table view, it isn't returning from the fetch results, despite the fact you said you have 3 sections. You can return it manually by:

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return 3;
}

Then

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{    
   if  ([[[self.fetchedResultsController sections] objectAtIndex:section] numberOfObjects] == 0){     
       return 1;
   } else {
       return [[[self.fetchedResultsController sections] objectAtIndex:section] numberOfObjects];
   }
}

In your cellForRowAtIndexPath: test for empty..

if ([[[self.fetchedResultsController sections] objectAtIndex:section] numberOfObjects] == 0){
cell.textLabel = @"No Entries";

}

Just a idea.

EDIT: Be careful, if you try to catch a index that isn't returned by the fetch, your app can crash.

Answer 2

You need to modify your numberOfRowsInSection function to check if there are no real rows for that section, and return 1 if that is the case (instead of 0).

Then, in the cellForRowAtIndexPath , check if you have data for that section, and just create your "no entries" cell when you see that you don't.