Why Is This Predicate Format Being Turned into '= Nil'

Why is this predicate format being turned into '= nil'

The %@ format expects a Foundation object as argument, the zero
is interpreted as nil.

You can convert the integer to NSNumber:

let filterPredicate = NSPredicate(format: "uid = %@", weightUnitFilter as NSNumber)

or use the "long int" format instead:

let filterPredicate = NSPredicate(format: "uid = %ld", weightUnitFilter)

Invalid predicate: nil RHS for second argument in NSPredicate format

On all current iOS and OS X platforms, the C int is a 32-bit integer,
and that is what the %d format expects on the variable argument list.
If you pass a 64-bit integer then reading the next variable argument
will read the extra 4 zero bytes.

The following table shows which format is for which integer type:

  Format   C type          Swift type
  -----------------------------------
  %d       int             Int32
  %ld      long int        Int
  %lld     long long int   Int64

and similarly for the unsigned types.

Alternatively, convert the integer to a NSNumber object and use
the %@ format, this works
for integers of all sizes. Example:

let value = 1234
let predicate = NSPredicate(format: "value = %@", value as NSNumber)

NSInvalidArgumentException', reason: 'Invalid predicate: nil RHS, need help figuring this out

The error message indicates that searchString is nil in

NSPredicate *filterPredicate = [NSPredicate 
            predicateWithFormat:@"(workoutName CONTAINS[cd] %@)", searchString];

If the intention is to display all objects if no search string is given, you should
just not assign a predicate to the fetch request in that case:

if ([searchString length] > 0) {
    NSPredicate *filterPredicate = [NSPredicate 
            predicateWithFormat:@"(workoutName CONTAINS[cd] %@)", searchString];
    [request setPredicate:filterPredicate];
}

NSPredicate crash after swift 3 migration

The %@ format expect a Foundation object as argument, compare
"Predicate Format String Syntax" in the "Predicate Programming Guide".

You can bridge the Int64 to NSNumber:

let id = Int64.max
let predicate = NSPredicate(format: "id == %@", id as NSNumber)
print(predicate) // id == 9223372036854775807

or change the format to "long long":

let id = Int64.max
let predicate = NSPredicate(format: "id == %lld", id)
print(predicate) // id == 9223372036854775807

Bridging all number types to NSNumber is possible as of Swift 3.0.1 (Xcode 8.1) with the implementation of
SE-0139 Bridge Numeric Types to NSNumber and Cocoa Structs to NSValue.

Core data query value is not nil is not returning object with value equal 0

try predicate like this

myPredicate = NSPredicate(format: "rawValue != nil")

Trying to pop a UIAlert if my search predicate returns nil

Ha ha! Got it...

- (void)searchBarSearchButtonClicked:(UISearchBar *)searchBar {

    if (self.sBar.text != nil) {

        NSPredicate *template = [NSPredicate predicateWithFormat:@"name contains[cd] $SEARCH OR optionOne contains[cd] $SEARCH OR optionTwo contains[cd] $SEARCH"];
        NSDictionary *replace = [NSDictionary dictionaryWithObject:self.sBar.text forKey:@"SEARCH"];
        NSPredicate *predicate = [template predicateWithSubstitutionVariables:replace];

        [fetchedResultsController.fetchRequest setPredicate:predicate];

    }

    NSError *error = nil;
    if (![[self fetchedResultsController] performFetch:&error]) {

        // Handle error
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        exit(-1);  // Fail
    } 

    if ([[fetchedResultsController fetchedObjects] count] != 0)  {

        [self.myTable reloadData];
        [sBar resignFirstResponder];  

    }
    else {

        //display alert
            UIAlertView *alert = [[UIAlertView alloc] initWithTitle:nil message:@"No records match." 
                                                           delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
            [alert show];
            [alert release];

    }   
}

NSPredicate equals nil in NSFetchRequest

Make sure that your fetchRequest.predicate value is set (i.e., is not nil).

The code in your post does show that the predicate value is assigned. However, when the NSFetchRequest.predicate attribute is not set then the println console message will display ((null)) for the predicate value.

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