Fetch only the UniqueID column and populate array - iphone

Question

I'm using the code below to populate an array from my ManagedObjectContext, but what I would like to do is to fetch only the unique ID numbers of each row matching my query (itemType = 1) and populate the fetchResults array with only these unique ID numbers. Is that possible?
Any help is appreciated.
lq
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:[NSEntityDescription entityForName:#"MyAppName"
inManagedObjectContext:[self managedObjectContext]]];
NSError *error = nil;
NSPredicate *predicate;
NSArray *fetchResults;
predicate = [NSPredicate predicateWithFormat:#"(itemType = %i)", 1];
[request setPredicate:predicate];
fetchResults = [managedObjectContext executeFetchRequest:request error:&error];
if (!fetchResults) {
// NSLog(#"no fetch results error %#", error);
}
self.mutableArrayName = [NSMutableArray arrayWithArray:fetchResults];
[request release];

Answer 1

To help anyone with similar needs, I'm answering my own question. I figured out a solution that works for pulling specific row and/or column data from my SQLite database in query form, rather than using Fetch with Predicate. (Note: code shows examples for extracting string and integer data types.)
First, add a Framework for libsqlite3.0.dylib
In the header add the following file:
#import <sqlite3.h>
#interface MyViewController : UIViewController {
NSMutableArray *dataArray; // This array will hold data you will extract
NSArray *summaryArray; // This holds an array of PKIDs that will be queried
}
#property (nonatomic, retain) NSMutableArray *dataArray;
#property (nonatomic, assign) NSArray *summaryArray;
- (void)getData:(NSInteger *)intPKID;
- (NSString *) getDBPath;
#end
In the implementation file add the following:
static sqlite3 *database = nil; // add this before the #implementation line
#synthesize dataArray;
#synthesize summaryArray;
- (NSString *) getDBPath {
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory , NSUserDomainMask, YES);
NSString *documentsDir = [paths objectAtIndex:0];
return [documentsDir stringByAppendingPathComponent:#"MyDatabaseName.sqlite"];
}
- (void)getData:(NSInteger *)intPKID {
NSString *dbPath = [self getDBPath];
if (sqlite3_open([dbPath UTF8String], &database) == SQLITE_OK) {
NSString *strSQL;
NSString *strExtractedData;
NSUInteger count;
NSInteger intPK;
if (self.dataArray == nil) {
self.dataArray = [[[NSMutableArray alloc] init] autorelease];
} else {
[self.dataArray removeAllObjects];
}
count = [self.summaryArray count];
for (NSUInteger i = 0; i < count; ++i) {
// Extract a specific row matching a PK_ID:
strSQL = [NSString stringWithFormat: #"select intPKID, strColumnName from MyDatabaseName where (PKID = %i)", [[self.summaryArray objectAtIndex:i]intValue]];
// Extract a range of rows matching some search criteria:
// strSQL = [NSString stringWithFormat: #"select intPKID, strColumnName from MyDatabaseName where (ITEMTYPE = '%i')", 1];
const char *sql = (const char *) [strSQL UTF8String];
sqlite3_stmt *selectstmt;
if(sqlite3_prepare_v2(database, sql, -1, &selectstmt, NULL) == SQLITE_OK) {
while(sqlite3_step(selectstmt) == SQLITE_ROW) {
[self.dataArray addObject:[NSNumber numberWithInt:qlite3_column_int(selectstmt, 0)]];
[self.dataArray addObject:[NSString stringWithUTF8String:(char *)sqlite3_column_text(selectstmt, 1)]];
}
}
}
} else {
sqlite3_close(database); // Database not responding - close the database connection
}
}

Answer 2

predicate = [NSPredicate predicateWithFormat:#"itemType == 1"];
or
predicate = [NSPredicate predicateWithFormat:#"(itemType == %i)", 1];
should both work.