ios – 通过索引访问数组对象导致 – [_ NSFaultingMutableSet objectAtIndex：]：

所以我在这里有函数collectionView：cellForItemAtIndexPath：

func collectionView(collectionView: UICollectionView,cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCellWithReuseIdentifier("cellID",forIndexPath: indexPath)
        print("Creating collection view number: \(indexPath.row)")
        // Configure the cell
        cell.backgroundColor = UIColor.lightGrayColor()
        let thing = Mirror(reflecting: annotation?.photos!)
        print(thing.subjectType)
        print(annotation?.photos![indexPath.row])
        return cell
}

这是我的注释对象和照片对象的声明

class CustomAnnotation : NSManagedobject,MKAnnotation {
    @NSManaged var latitude: NSNumber
    @NSManaged var longitude : NSNumber
    @NSManaged var title : String?
    @NSManaged var subtitle: String?
    @NSManaged var photos : [Photo]?

    var coordinate = CLLocationCoordinate2D()

    override init(entity: NSEntityDescription,insertIntoManagedobjectContext context : NSManagedobjectContext?) {
        super.init(entity: entity,insertIntoManagedobjectContext: context)
    }

    init(coordinate : CLLocationCoordinate2D,context: NSManagedobjectContext) {
        let entity = NSEntityDescription.entityForName("CustomAnnotation",inManagedobjectContext: context)!
        super.init(entity: entity,insertIntoManagedobjectContext: context)
        self.longitude = coordinate.longitude
        self.latitude = coordinate.latitude
        print(photos)
    }

    func setCoordinate() {
        self.coordinate.longitude = CLLocationdegrees(self.longitude)
        self.coordinate.latitude = CLLocationdegrees(self.latitude)
    }
}

class Photo : NSManagedobject {

    @NSManaged var imagePath : String
    @NSManaged var customAnnotation : CustomAnnotation

    override init(entity: NSEntityDescription,insertIntoManagedobjectContext context: NSManagedobjectContext?) {
        super.init(entity: entity,insertIntoManagedobjectContext: context)
    }
    init(imagePath: String,context : NSManagedobjectContext) {
        let entity = NSEntityDescription.entityForName("Photo",insertIntoManagedobjectContext: context)
        self.imagePath = imagePath

    }
}

这就是我如何保存与CustomAnnotation类具有反多对一关系的Photos对象

if (annotation?.photos)!.isEmpty {
            // Load photos
            print("downloading photos")
            dispatch_async(dispatch_get_main_queue()) {
                FlickrClient.sharedInstance().getFlickrImages(self) {(result,success,errorString) in
                    if success {
                        print("loading photos")

                        // Use the inverse relationship to save the data
                        for photoURL in result as! [String] {
                            let photo = Photo(imagePath: photoURL,context: self.sharedContext)
                            photo.customAnnotation = self.annotation!
                            print(photo.imagePath)
                        }
                        dispatch_async(dispatch_get_main_queue()) {
                            self.collectionView!.reloadData()
                        }
                        CoreDataStackManager.sharedInstance().saveContext()


                    }
                    else {
                        self.showAlert("Error",message: errorString!,confirmButton: "OK")
                    }
                }
            }
        }

这是崩溃时发生的事情的日志：

Creating collection view number: 0

Optional <Array<Photo>> 

2015-12-27 00:15:07.046 VirtualTourist[10413:1965722] -[_NSFaultingMutableSet objectAtIndex:]: unrecognized selector sent to instance 0x7f956d4d8cf0

2015-12-27 00:15:07.058 VirtualTourist[10413:1965722] *** Terminating app due to uncaught exception 'NSinvalidargumentexception',reason: '-[_NSFaultingMutableSet objectAtIndex:]: unrecognized selector sent to instance 0x7f956d4d8cf0'

我不明白为什么print(注释？.photos！[indexPath.row])崩溃我的程序.我在线阅读,它说这是对象是NSSet但是注释的结果？.photo！是一个阵列.所以我有点卡住,有什么提示吗？

解决方法

我已经解决了,因为在我的数据模型中我选择了CustomAnnotation实体中的照片关系是无序的,即使在类定义中照片变量是一个数组,也总是返回NSSet.

我需要做的就是将Arranged设置为Ordered：

一切正常,返回一个Array而不是NSSet