Swift: Search for string in core data model

Question

I'm confronted with the following problem in Swift.

I wrote the following function to retrieve all persons in my model with the name "David".

private func myFetchRequest()
{
    let moc = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext

    let myRequest = NSFetchRequest(entityName: "RegisterOfPersons")

    myRequest.predicate = NSPredicate(format: "name = %@", "David")

    do{
        let results = try moc.executeFetchRequest(myRequest)

        for result in results
        {
             print(result)
        }

    } catch let error{
        print(error)
    }
}

Even though my model contains two entries with the attribute name = "David", the line

myRequest.predicate = NSPredicate(format: "name = %@", "David")

does not find these entries, because "name" is an optional attribute in my model. Do I have to search for Optional("David"), meaning something like myRequest.predicate = NSPredicate(format: "name = %@", Optional("David"))?

How can I search for all entries with the name "David" in my model? What am I doing wrong?

Thanks for your help!

Not sure, but having `name` be an optional attribute is not related. Swift optionals are not the same thing as Core Data optional attributes. — Tom Harrington, Aug 08 '16 at 15:31
Does the literal syntax `NSPredicate(format: "name = 'David'")` work ? — vadian, Aug 08 '16 at 15:34

Nirav D · Accepted Answer · 2016-08-08T15:56:34.337

12

You are predicating with string so enclose your comparison name with single quote like this

myRequest.predicate = NSPredicate(format: "name = '%@'", "David")

Also try with Contains

myRequest.predicate = NSPredicate(format: "name CONTAINS[cd] %@", "David")

edited Aug 08 '16 at 15:56

answered Aug 08 '16 at 15:20

Nirav D

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This will compare with the literal string %@. From the predicate programming guide "If you use variable substitution using %@ (such as firstName like %@), the quotation marks are added for you automatically." – pbasdf Aug 08 '16 at 15:27
@pbasdf I know that but op is using `=` that is the reason suggesting to op to add Single Quote. – Nirav D Aug 08 '16 at 15:29
Thank you so much for your answer! I tried as you suggested. However, it still doesn't work. Maybe I am making a mistake somewhere else? – Pisan Aug 08 '16 at 15:31
1

Is you property name contains David or exact David, if it is contains than you need to use `CONTAINS[C]` instead of `=`. – Nirav D Aug 08 '16 at 15:34
Check my edited answer, and give reply is it working or not? – Nirav D Aug 08 '16 at 15:57
Thank you very much NDoc! Thanks to your post I found out that the name in the database contained a spelling miss! Thanks for your help guys! – Pisan Aug 08 '16 at 16:26
Welcome mate, Happy coding :) – Nirav D Aug 08 '16 at 16:38

Swift: Search for string in core data model

1 Answers1