Question

In Xcode 3.X, you were supposed to right-click the whitespace in the fetch request template’s predicate editor to specify a variable input rather than a hard-coded predicate.

Where is this in XCode 4? I’ve held option, right-clicked, option-clicked, etc and cannot figure it out….

Answer 1

I don’t think X4 has the variable anymore.

Instead, I think you have to choose an expression and then provide a variable of the form $VARNAME.

For example, given and entity Alpha with an attribute aString, I created a fetch request template bobFetch with an expression of aString == $TESTVAR.

Alpha *a=[NSEntityDescription insertNewObjectForEntityForName:@"Alpha" inManagedObjectContext:self.moc];
a.aString=@"steve";
[self saveContext];
NSDictionary *subVars=[NSDictionary dictionaryWithObject:@"steve" forKey:@"TESTVAR"];
NSFetchRequest *fetchRequest =   [self.managedObjectModel fetchRequestFromTemplateWithName:@"bobRequest" substitutionVariables:subVars];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Alpha" inManagedObjectContext:self.moc];
[fetchRequest setEntity:entity];

If logged fetchRequest reports:

<NSFetchRequest: 0x4d17480> (entity: Alpha; predicate: (aString == "steve"); sortDescriptors: ((null)); type: NSManagedObjectResultType; )

… and can then be used normally.

NSError *error = nil;
NSArray *fetchedObjects = [self.moc executeFetchRequest:fetchRequest error:&error];
if (fetchedObjects == nil) {
    NSLog(@"fetch error = %@",error);
}
NSLog(@"fetchObjects = %@",fetchedObjects);

Kind of clumsy for a graphical environment but it works.