CODEWITHSUNDEEP
swiftcore-datansmanagedobject
Duck
Duck

Reputation: 35953

How do I use this fetchRequest() in Swift?

I am new to swift. I am trying to create a core data NSManagedObject class as I used to do in Objective-C.

In Objective-C I would create something like

+ (Countries *)countryWithName:(NSString *)name
 inManagedObjectContext:(NSManagedObjectContext *)context {

  NSFetchRequest *request = [[NSFetchRequest alloc] init];
  request.entity = [NSEntityDescription entityForName:NSStringFromClass([self class])
                               inManagedObjectContext:context];


  NSPredicate *predicate = [NSPredicate predicateWithFormat:
                            @"(country == %@)", name];

  request.predicate = predicate;

  return [[context executeFetchRequest:request error:nil] lastObject];
}

So, at any time I would like to fetch a country by name on core data, I would do

userCountry = [Countries countryWithName:@"United States" inManagedObjectContext:self.managedObjectContext];

But after creating a NSManagedObject class using swift, I see Xcode created this code inside Countries+CoreDataProperties.swift

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

@NSManaged public var number: Int16
@NSManaged public var name: String?
@NSManaged public var shortcut: NSData?

Now I want to create my class countryByName function. The first line there should be

let fetchRequest = NSFetchRequest(entityName: "Countries")

but fetchRequest() is already created.

how do I use that?

it will not let me use

let request = Countries.fetchRequest()

giving me an error Ambiguous use of fetchRequest)=

Upvotes: 3

Views: 3838

Answers (2)

Kon
Kon

Reputation: 4099

Fetch request is a generic so you must specify the type, like so:

let request: NSFetchRequest<Countries> = Countries.fetchRequest()

Upvotes: 4

vadian
vadian

Reputation: 285082

You are using two different entities Countries and Atributos in the fetchRequest() declaration. That indeed ambiguous. The entity must be unique.

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

and you have to use it

let fetchRequest : NSFetchRequest<Countries> = Countries.fetchRequest()

Note: It's highly recommended to name entities in singular form. Semantically each record represents one Country not one Countries. Only to-many relationships are supposed to be named in plural form.

Upvotes: 4

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