executeFetchRequest throw fatal error: NSArray element failed to match the Swift Array Element type

Question

I'm testing swift with CoreData and I created the following code:

import UIKit
import CoreData

class Contact: NSManagedObject {

    @NSManaged var name: String
    @NSManaged var email: String

    class func execute(){
        let appDel:AppDelegate = (UIApplication.sharedApplication().delegate as AppDelegate)
        let context:NSManagedObjectContext = appDel.managedObjectContext!

        let entityDescripition = NSEntityDescription.entityForName("Contact", inManagedObjectContext: context)
        let contact = Contact(entity: entityDescripition!, insertIntoManagedObjectContext: context)

        contact.name = "john Apleesee"
        contact.email = "[email protected]"

        context.save(nil)

        let fetch:NSFetchRequest = NSFetchRequest(entityName: "Contact")
        var result = context.executeFetchRequest(fetch, error: nil) as [Contact]

        let firstContact = result[0] as Contact  //  <<-- error !

        println("\(firstContact.name)")
        println("\(firstContact.email)")

    }

}

When I run:

Contact.execute()

Then the compiler throw this error:

fatal error: NSArray element failed to match the Swift Array Element type

when I try to get values from array:

 let firstContact = result[0] as Contact

I guess the problem is in executeFetchRequest. On Objective-c the return type of executeFetchRequest is a NSArray. Now on Swift the return type is a [AnyObject]?.

I tried to cast the [AnyObject]? result to NSArray, but Xcode said:

 Cannot convert the expression's type '[AnyObject]?' to type 'NSArray'

What I'm doing wrong ?

I'm using: Xcode 6.0 (6A313) GM and OSX 10.9.4

Update:
-----------

If I get executeFetchRequest result as an optional array and use [NSManagedObject] instead of [Contact] it works.

if let result: [NSManagedObject]? = context.executeFetchRequest(fetch, error: nil) as? [NSManagedObject] {

        let firstContact: NSManagedObject = result![0]

        let name = firstContact.valueForKey("name") as String
        let email = firstContact.valueForKey("email") as String

        println("\(name)")
        println("\(email)")
    }

Update2:
-----------

This kind of problem occurs when entity instances didn't get loaded using your NSManagedObject class. There are a few different reasons why that happens, all of which focus on "Core Data couldn't find the class you specified for that entity on the class line in the data model."

Among the possibilities:
- You specified the wrong package for your Swift class
- You forgot to specify the class
- You misspelled the name

In my case was I forgot to specify the class as POB shows in her answer.

Why did you set the -execute: method that performs a NSFetchRequest inside your NSManagedObjectsubclass? — Imanou Petit
– Imanou Petit, Commented Sep 17, 2014 at 21:14
I did it for the matter of simplicity. An easy way to show the problem here. — Sebastian
– Sebastian, Commented Sep 17, 2014 at 21:25
Did you try using let contact = NSEntityDescription.insertNewObjectForEntityForName("Contact", inManagedObjectContext: context) as Contact instead of let contact = Contact(entity: entityDescripition!, insertIntoManagedObjectContext: context)? — Imanou Petit
– Imanou Petit, Commented Sep 17, 2014 at 22:14
I guess the problem is in executeFetchRequest. On Objective-c the return type of executeFetchRequest is a NSArray. Now on Swift the return type is a [AnyObject?]. — Sebastian
– Sebastian, Commented Sep 18, 2014 at 13:08

Imanou Petit · Accepted Answer · 2014-09-18 17:24:38Z

35

I was able to reproduce your error message in the console. You get this message because you didn't set correctly your entity class name in the Core Data Model Editor (see image below).

enter image description here

Once done, you will be able to use your original code with Contact subClass. You can learn more about Core Data and namespaces here.

answered Sep 18, 2014 at 17:24

Imanou Petit

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1 Comment

Arun Kumar P Over a year ago

in that class field, I can't add "."

Danboz · Accepted Answer · 2018-04-27 04:46:12Z

6

In my case, i changed the Module as "Current Product Module" inside Core Data Model Editor.It started working fine for me.

edited Apr 27, 2018 at 4:46

answered Dec 3, 2015 at 7:49

Danboz

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Comments

Community · Accepted Answer · 2017-05-23 10:33:44Z

1

I think its bad idea to set prefix of your target name like this Because if you would like to move your model into other app, or change targer name you will end up with changing it again,

So there is another way. If you look at how xcode generates core data entities now, as @A_man said you need to set current module in editor and use @objc() like this :

import CoreData

@objc(Contact)
class Contact: NSManagedObject {
    @NSManaged var name: String?
    @NSManaged var email: String?
}

And field has to be optional because they can be nil

edited May 23, 2017 at 10:33

CommunityBot

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answered Dec 3, 2015 at 8:46

Serg Dort

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1 Comment

aumansoftware Jan 18 at 1:52

This is the same mapping as the automated class generation in coredata. Should be the top answer and is still relevant in '25

Subhash · Accepted Answer · 2016-05-17 08:45:23Z

1

Check the class and module in Entity from Data Model Inspector and set the class name as entity name and module as 'Current Product Module' Class name and Module

answered May 17, 2016 at 8:45

Subhash

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Comments

Surrey · Accepted Answer · 2014-09-18 13:36:37Z

-1

I think your problem is that executeFetchRequest gives back an optional array, not an array. You need to unwrap it.

if let result: [Contact]? = context.executeFetchRequest(fetch, error: nil) as? [Contact] {

    let firstContact = result[0]

    println("/(firstContact.name)")
    println("/(firstContact.email)")
}

answered Sep 18, 2014 at 13:36

Surrey

1

1 Comment

Sebastian Over a year ago

Thanks for the answer Surrey! It was no working with Contact, but If I use NSManageObject instead of Contact it runs. Don't ask me why ! :)

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