I have dbobject like:
#import <Foundation/Foundation.h>
#import <DBAccess/DBAccess.h>
@interface GroupMember : DBObject
@property (strong) NSString *firstname;
@property (strong) NSString *lastname;
@property (strong) NSString *_id;
@end
How can I get an array of all group member's firstname?
Because you are not dealing with SQL but with whole objects, this requires a little bit of working round the problem, but it is possible.
NSDictionary* resultsGroupedByFirstName = [[GroupMember query] groupBy:@"firstname"];
NSArray* names = resultsGroupedByFirstName.allKeys;
This is a fairly expensive call as it is having to do a fair amount of work in the background. Although it is optimised slightly by using an index to detect changes in the column.
This should do the trick.
NOTE:
DBAccess v1.6.7 now has a distinct call thanks to your question and feedback. http://www.db-access.org/downloads