How to use predicates with fetchRequest in Core Data

Question

I pass a contact Identifier from Contacts tableview controller to another Location tableview controller. So I define a delegate ContactSelectionDelegate and implement metho

Answer 1

First of all get rid of all NSString and NSDictionary occurrences. This is Swift!. Use the Swift native structs String and Dictionary.

Second of all put always all good code in the do scope of a do - catch block.

A CoreData predicate has a simple format attribute == value which is very similar to aContact.uniqueId! == contactIdentifierString:

var contactIdentifierString = ""

func userSelectedContact(contactIdentifier: String) {

    let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

    do {
        let fetchRequest : NSFetchRequest<Contact> = Contact.fetchRequest()
        fetchRequest.predicate = NSPredicate(format: "uniqueId == %@", contactIdentifier)
        let fetchedResults = try context.fetch(fetchRequest) as! [Contact]
        if let aContact = fetchedResults.first {
           providerName.text = aContact.providerName
        }
    }
    catch {
        print ("fetch task failed", error)
    }

}

The code assumes that there is a NSManagedObject subclass Contact containing

@nonobjc public class func fetchRequest() -> NSFetchRequest<Contact> {
    return NSFetchRequest<Contact>(entityName: "Contact")
}