Question

I’m currently working on an app that uses Core Data. The issue I’m dealing with is the fetch data with predicate, example shown below:

[[self managedObjectContext] fetchObjectsForEntityName:@"Employee" withPredicate:
@"(lastName LIKE[c] 'Worsley') AND (salary > %@)", minimumSalary];

What i want to do is fetch the number of different categories from a certain dataset like this:

Entity Person:

-Name (String)

-Location (String)

-Age (Int)

So if for example i have 3 samples in the dataset:
[Lisa, Sweden, 30] [Mike, USA, 24] [Jacob, England, 28]

I now want to fetch the number of different locations, is this possible?

Many Thanks

Robert

Answer 1

In the FetchResults controller method,add the following code.

[fetchRequest setReturnsDistinctResults:YES];

[fetchRequest setResultType:NSDictionaryResultType];

[fetchRequest setPropertiesToFetch:[NSArray arrayWithObject:[entityProperties objectForKey:@"value"]]];

From the documentation of returnsDistinctResults:

This value is only used if a value has been set for propertiesToFetch.

From the documentation of propertiesToFetch:

This value is only used if resultType is set to NSDictionaryResultType.

From the documentation of resultType:

The default value is NSManagedObjectResultType.