Question

我正在研究Udacity上的CoreData项目，并且很难实现fetchedResultsController。我尝试使用lazy var实例化fetchedResultsController，但它提示我＆＃34;实例成员上下文不能用于类型＆＃39; ViewController＆＃39;。我的代码是这样的：

//AppDelegate
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?
    let stack = CoreDataStack(modelName: "Model")
    ... 
}

//ViewController
class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate, MKMapViewDelegate{

    lazy var context: NSManagedObjectContext = {
        let appDelegate = UIApplication.shared.delegate as! AppDelegate
        return appDelegate.stack!.context
    }()

    lazy var fetchedResultsController: NSFetchedResultsController<NSFetchRequestResult> = {
        let fetchedRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Photo")
        fetchedRequest.sortDescriptors = []

        return NSFetchedResultsController(fetchRequest: fetchedRequest, managedObjectContext: context, sectionNameKeyPath: nil, cacheName: nil)
    }()

这样做会在＆＃39;上下文中给出错误信息。在fetchedResultsController中指示：

实例成员＆＃39; context＆＃39;不能在类型＆＃39; ViewController＆＃39;
上使用

我有什么不对的吗？非常感谢任何建议，谢谢！

Answer 1

在lazy属性中引用self时，您需要明确使用context：

return NSFetchedResultsController(fetchRequest: fetchedRequest, managedObjectContext: self.context, sectionNameKeyPath: nil, cacheName: nil)

Swift fetchResultsController：实例成员不能用于类型＆＃39; ViewController＆＃39;

1 个答案: