Question

I have something like this on my core data class to fetch all data of kind “dataX” from the database, as an array…

+ (NSArray *)allDataInManagedObjectContext:(NSManagedObjectContext *)context
{
    NSArray *allData = nil;

    NSFetchRequest *request = [[NSFetchRequest alloc] init];

    request.entity = [NSEntityDescription entityForName:@"myData" inManagedObjectContext:context];

    [request setResultType:NSDictionaryResultType];
    [request setReturnsDistinctResults:YES];
    [request setPropertiesToFetch:[NSArray arrayWithObject:@"dataX"]];

    NSError *error = nil;
    allData = [context executeFetchRequest:request error:&error];
    [request release];

    return allData;
}

The problem is that this returns an array of dictionaries and in this case, each dictionary contains just one pair object/key.

As all the keys on all dictionaries on that array are equal to “dataX”, I would like to receive, instead, an array containing just the values… so instead of this

array { dictionary1, dictionary2...
dictionary1 = one object for key "dataX" (lets call it object1)
dictionary2 = one object for key "dataX" (lets call it object2)
etc...

I would like to receive this

array {object1, object2, ... 

is there a way to do that in the fetch itself?

thanks

Answer 1

+ (NSMutableArray *)allDataInManagedObjectContext:(NSManagedObjectContext *)context
{
    NSMutableArray *allData = [NSMutableArray array];

    NSMutableArray *returnableArray=[NSMutableArray array];
    NSFetchRequest *request = [[NSFetchRequest alloc] init];

    request.entity = [NSEntityDescription entityForName:@"myData" inManagedObjectContext:context];

    [request setResultType:NSDictionaryResultType];
    [request setReturnsDistinctResults:YES];
    [request setPropertiesToFetch:[NSArray arrayWithObject:@"dataX"]];

    NSError *error = nil;
    allData = [[context executeFetchRequest:request error:&error] mutableCopy];
    [request release];

   for(int i=0;i<[allData count];i++)
   {
     [returnableArray addObject:[[allData objectAtIndex:i] valueForKey:@"dataX"]];
   }
    return returnableArray;
}

use this.