How to apply the type to a NSFetchRequest instance?

In Swift 2 the following code was working:

let request = NSFetchRequest(entityName: String)

but in Swift 3 it gives error:

Generic parameter "ResultType" could not be inferred

because NSFetchRequest is now a generic type. In their documents they wrote this:

let request: NSFetchRequest<Animal> = Animal.fetchRequest

so if my result class is for example Level how should I request correctly?

Because this not working:

let request: NSFetchRequest<Level> = Level.fetchRequest

let request: NSFetchRequest<NSFetchRequestResult> = Level.fetchRequest()

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

depending which version you want.

You have to specify the generic type because otherwise the method call is ambiguous.

The first version is defined for NSManagedObject, the second version is generated automatically for every object using an extension, e.g:

extension Level {
    @nonobjc class func fetchRequest() -> NSFetchRequest<Level> {
        return NSFetchRequest<Level>(entityName: "Level");
    }

    @NSManaged var timeStamp: NSDate?
}

The whole point is to remove the usage of String constants.

I think i got it working by doing this:

let request:NSFetchRequest<NSFetchRequestResult> = NSFetchRequest(entityName: "Level")

at least it saves and loads data from DataBase.

But it feels like it is not a proper solution, but it works for now.

The simplest structure I found that works in 3.0 is as follows:

let request = NSFetchRequest<Country>(entityName: "Country")

where the data entity Type is Country.

When trying to create a Core Data BatchDeleteRequest, however, I found that this definition does not work and it seems that you'll need to go with the form:

let request: NSFetchRequest<NSFetchRequestResult> = Country.fetchRequest()

even though the ManagedObject and FetchRequestResult formats are supposed to be equivalent.

How to apply the type to a NSFetchRequest instance?

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