tc_insertIntoContext.m

@implementation NSManagedObject (TCCreation)
+ (instancetype)tc_insertIntoContext:(NSManagedObjectContext*)ctx
{
    for(NSEntityDescription *desc in [ctx.persistentStoreCoordinator.managedObjectModel entities]) {
        if([desc.managedObjectClassName isEqual:NSStringFromClass(self)]) {
            return [[self alloc] initWithEntity:desc insertIntoManagedObjectContext:ctx];
        }
    }
    NSAssert(NO, @"This class does not exist in the managed object model for %@", ctx);
    return nil;
}
@end

tc_insertIntoContext.swift

extension NSManagedObject {
    class func tc_insertIntoContext(context: NSManagedObjectContext) -> Self?
    {
        let thisClassName : String = NSStringFromClass(self as! AnyClass)
        for desc in context.persistentStoreCoordinator!.managedObjectModel.entities as! [NSEntityDescription] {
            if desc.managedObjectClassName == thisClassName {
                return self(entity:desc, insertIntoManagedObjectContext:context)
            }
        }
        assert(false, "This class does not exist in the managed object model for \(context)")
        return nil;
    }
}

Thanks @nevyn.

Oops, I spoke too soon on the meetup page.

So, this here will compile:

extension NSManagedObject {

    class func tc_insertIntoContext(context: NSManagedObjectContext) -> AnyObject? {
        let thisClassName : String = NSStringFromClass(self as! AnyClass)
        for desc in context.persistentStoreCoordinator!.managedObjectModel.entities as! [NSEntityDescription] {
            if desc.managedObjectClassName == thisClassName {
                return self(entity:desc, insertIntoManagedObjectContext:context)
            }
        }
        assert(false, "This class does not exist in the managed object model for \(context)")
        return nil
    }
}

There are still some major drawbacks though:

1. Inserting a single entity is now an O(n) operation 😢
2. Not a designated initializer
3. We have to cast from AnyObject?
4. This is still very "Obj-C" ish