CODEWITHSUNDEEP
iosobjective-cxcodecore-data
A.D
A.D

Reputation: 2270

Fetch from core data where value contains string

I have a core data table called Forms which contains a attribute called objectids which holds a comma separated string with ids. (it can also contain just one id) ex.

objectids = "90"          // one id
objectids = "91,23,44"    // multiple ids

I receive a objectid and I want to match that and see if it exists as a value in any Forms -> objectids entry.

What is important is that it only matches whole string. ie. objectid: 1 should not match with objectids: 91, 23, 44, etc.

Here is a snippet of my code.

-(NSDictionary*)readForm:(NSString*)objectid
{

  ...

  NSManagedObjectContext *managedObjectContext = [self managedObjectContext];
  NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"Forms"];
  NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"added_date" ascending:NO];
  [fetchRequest setSortDescriptors:[NSArray arrayWithObject:sortDescriptor]];
  [fetchRequest setReturnsObjectsAsFaults:NO];
  fetchRequest.predicate = [NSPredicate predicateWithFormat:@"userid == %@ AND objectids == %@ AND active == %@", user.userid, objectid, @"yes"];

  // *** in this fetchRequest I want to include some snippet of code to:
  // *** Match string, but only whole string seperated by commas, unless it only has one value in which case it contains no commas.

  NSError *err = nil;
  NSArray *results = [managedObjectContext executeFetchRequest:fetchRequest error:&err];
  if([results count])
  {    
    ...
  }
}

I hope it's understandable.

I simply do not know enough of objective C to even know what terms to search for.

Any help is appreciated!

Upvotes: 1

Views: 2159

Answers (2)

ChiellieNL
ChiellieNL

Reputation: 103

Considering your example:

objectids = "90"          // one id
objectids = "91,23,44"    // multiple ids

In case there's only 1 id, you can compare the full string. In case there are more ids, they are always either preceded or followed by a comma.

Perhaps you can use something like this:

NSString *first = [NSString stringWithFormat:@"%@,%%", objectid];
NSString *last = [NSString stringWithFormat:@"%%,%@", objectid];
NSString *inBetween = [NSString stringWithFormat:@"%%,%@,%%", objectid];

fetchRequest.predicate = [NSPredicate predicateWithFormat:@"userid == %@ AND (objectids == %@ OR objectids LIKE %@ OR objectids LIKE %@ OR objectids LIKE %@) AND active == %@", user.userid, objectid, first, last, inBetween, @"yes"];

Which should make a statement like:

  • objectids IS exactly "90" OR
  • objectids starts with "90," OR
  • objectids ends with ",90" OR
  • objectids contains ",90,"

Upvotes: 1

George Brown
George Brown

Reputation: 1144

For string comparisons, you could use LIKE instead of ==, and also, for your bool, use a literal, @YES, so your predicate would be :

fetchRequest.predicate = [NSPredicate predicateWithFormat:@"userid == %@ AND objectids LIKE %@ AND active == %@", user.userid, objectid, @YES];

For more complex string comparisons, you could use a predicateWithBlock:

EDIT : reading your further comments, I think this question answers the exact same problem using regex : Form NSPredicate from string that contains id's

Upvotes: 2

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