I pass a contact Identifier from Contacts tableview controller to another Location tableview controller. So I define a delegate ContactSelectionDelegate and implement method userSelectedContact in Location tableview controller and get contactIdentifierString
I am searching the database to find a match for contactIdentifierString and find value for another attribute provider name. This involves searching the whole database. Is there a faster way by assigning a predicate to the context fetchRequest. I thought that would be faster and fewer lines of code.
Can someone suggest how to use predicates with contact fetchRequest?
ContactTableViewController code:
protocol ContactSelectionDelegate{
func userSelectedContact(contactIdentifier:NSString)
}
class ContactTableViewController: UITableViewController {
var delegate:ContactSelectionDelegate? = nil
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
if (delegate != nil){
let contactDict:NSDictionary = allContacts.object(at: indexPath.row) as! NSDictionary
let identifier = contactDict.object(forKey: "uniqueId")
delegate!.userSelectedContact(contactIdentifier: identifier as! NSString)
self.navigationController!.popViewController(animated: true)
}
}
}
LocationTableViewController code:
class LocationTableViewController: UITableViewController, ContactSelectionDelegate, CLLocationManagerDelegate {
var contactIdentifierString:NSString = NSString()
func userSelectedContact(contactIdentifier: NSString) {
var fetchedResults: [Contact] = []
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
do {
fetchedResults = try context.fetch(Contact.fetchRequest())
}
catch {
print ("fetch task failed")
}
if fetchedResults.count > 0 {
for contact in fetchedResults{
let aContact:Contact = contact
if (aContact.uniqueId! == contactIdentifierString as String) {
providerName.text = aContact.providerName
}
else {
continue
}
}
}
}
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)
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")
}