Sorting results in Obj-c - objective-c

Question

I need to be able to sort the results of my sort method, but it's unclear to me how to do that, do I need to just run a simular method again on the previous results or can it be done in one method?
Here's my method
-(NSArray*)getGameTemplateObjectOfType:(NSString *) type
{
NSArray *sortedArray;
if(editorMode == YES)
{
sortedArray = kingdomTemplateObjects;
}
else
{
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"type CONTAINS[cd] %#", type];
NSArray *newArray = [kingdomTemplateObjects filteredArrayUsingPredicate:predicate];
NSSortDescriptor *sortDescriptor;
sortDescriptor = [[NSSortDescriptor alloc] initWithKey:type
ascending:YES];
NSArray *sortDescriptors = [NSArray arrayWithObject:sortDescriptor];
sortedArray = [newArray sortedArrayUsingDescriptors:sortDescriptors];
}
return sortedArray;
}
type is being set to "Building" which returns all the building types in my game, but what if I then want those results sorted alphabetically according to their name? or perhaps sorted by which building is the most expensive from it's gold value?

Answer 1

You have to parse the array twice. NSPredicate does not provide a means to sort. Check out the NSPredicate Programming Guide. What I did actually was to quickly scan the NSPredicate BNF Syntax to look for obvious signs of sorting operators, such as ASC or DESC. Nothing is there.
Also, there are a number of similar questions here on SO:
How to sort NSPredicate
NSPredicate Sort Array and Order DESC
NSSortDescriptor and NSPredicate for sorting and filtering
To tell your getGameTemplateObjectOfType: how you want the results sorted, you might pass in some key for sorting. For example:
-(NSArray *)getGameTemplateObjectOfType:(NSString *)type sortedByKey:(NSString *)key ascending:(BOOL)ascending;
But to do so would likely complicate your code - you will have to handle all combinations of key and type inside your function. (Let me know if you don't understand what I'm saying here).
In the end it may be that you resign your filtering function getGameTemplateObjectOfType: to just that: filtering. And if the client of that function wants the results sorted in some fashion, then the client can do so. And then you will discover why it is that Apple has kept the functionalities separated.

Answer 2

in your code, if [kingdomTemplateObjects filteredArrayUsingPredicate:predicate]; returns the correct results
then you can use [newArray sortedArrayUsingSelector:#selector(localizedCaseInsensitiveCompare:)]; to sort your array.
-(NSArray*)getGameTemplateObjectOfType:(NSString *) type
{
NSArray *sortedArray;
if(editorMode == YES)
{
sortedArray = kingdomTemplateObjects;
}
else
{
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"type CONTAINS[cd] %#", type];
NSArray *newArray = [kingdomTemplateObjects filteredArrayUsingPredicate:predicate];
sortedArray = [newArray sortedArrayUsingSelector:#selector(localizedCaseInsensitiveCompare:)];
}
return sortedArray;
}