ios - 如何在 Swift 中从核心数据中获取 NSSet

Question

我有一个 Person 类和一个 Brand 类，它们是 Core Data 中的关系。我知道如何获取整个 Person 类 (NSManagedObject)，但我如何深入了解以仅获取与此人关联的品牌？

    import Foundation
    import CoreData

    class Person: NSManagedObject {

        @NSManaged var name: String
        @NSManaged var brands: NSSet

        func addBrandsObject(value: Brand) {
            self.mutableSetValueForKey("brands").addObject(value)
        }

    }

import Foundation
import CoreData

class Brand: NSManagedObject {

    @NSManaged var name: String
    @NSManaged var people: NSSet


}

View Controller :

![import UIKit
import CoreData

    class BrandsTableTableViewController: UITableViewController {


        var brands = \[NSManagedObject\]()
        var selectedPerson: Person?
        var selectedBrand: Brand?

        //Fetch Core Data
        override func viewWillAppear(animated: Bool) {
            super.viewWillAppear(animated)
            self.fetchCoreData()
        }

        //Helper Function to Fetch Core Data
        func fetchCoreData() {
            //1
            let appDelegate =
            UIApplication.sharedApplication().delegate as! AppDelegate

            let managedContext = appDelegate.managedObjectContext!

            //2
            let fetchRequest = NSFetchRequest(entityName:"Person")

            //3
            var error: NSError?

            let fetchedResults =
            managedContext.executeFetchRequest(fetchRequest,
                error: &error) as? \[NSManagedObject\]

            if let results = fetchedResults {
                ////what here? 
            } else {
                println("Could not fetch \(error), \(error!.userInfo)")
            }
        }][1]

Answer 1

因为你已经有了 person 实例，只需访问关系:

    for person in results {
        let brandSet = person.brands
    }

无需提取。

这当然假设您从 Person 到 Brand 的关系称为 brands。

还会有一些转换，没有转换就不能快速......