Intermediate Fetching - Core Data - page 90

var sd = NSSortDescriptor (key: "priceInfo.priceCategory" ,
ascending: true )
return sd
}()
The way to add sorts is very similar to the way you added filters. Each sort maps to
one of these three lazy NSSortDescriptor properties.
To initialize an instance of NSSortDescriptor you need three things: a key path to
specify the attribute by which you want to sort, a specification of whether the sort
is ascending or descending and an optional selector.
Note: If you've worked with NSSortDescriptor before, then you probably know
there's a block-based API that takes a comparator instead of a selector.
Unfortunately, Core Data doesn't support this way of defining a sort
descriptor.
The same thing goes for the block-based way of defining an NSPredicate . Core
Data doesn't support this either. The reason is related to the fact that
filtering/sorting happens in the SQLite database, so the predicate/sort
descriptor has to match nicely to something that can be written as an SQLite
statement.
The three sort descriptors are going to sort by name, distance and price category,
respectively, and they are all ascending. Before moving on, take a closer look at the
first sort descriptor, nameSortDescriptor . The initializer takes in an optional selector
called localizedStandardCompare . What is that?
Any time you're sorting user-facing strings, Apple recommends that you pass in
localizedStandardCompare to sort according to the language rules of the current
locale. That means the sort will “just work” and do the right thing for languages
with accented characters, for example. It's the little things that matter. :]
Next, go down to didSelectRowAtIndexPath and add the following cases to the end
of the switch statement:
//Sort By section
case nameAZSortCell :
selectedSortDescriptor = nameSortDescriptor
case nameZASortCell :
selectedSortDescriptor =
nameSortDescriptor . reversedSortDescriptor
as ? NSSortDescriptor
case distanceSortCell :
selectedSortDescriptor = distanceSortDescriptor
case priceSortCell :