如何在iOS 10 Swift 3中初始化NSFetchedResultsController [英] How to initialize a NSFetchedResultsController in iOS 10 Swift 3

问题描述

我无法使用Swift 3在iOS 10中初始化NSFetchedResultsController。

I can't get my NSFetchedResultsController initialized in iOS 10 using Swift 3.

let request = NSFetchRequest<NasaPicture>(entityName:"NasaPicture")  
request.predicate = Predicate(format: "isPagedResult == YES")  
request.sortDescriptors = [SortDescriptor(key: "date", ascending: false)]  
fetchedResultsController = NSFetchedResultsController(fetchRequest: request, managedObjectContext: moc, sectionNameKeyPath: nil, cacheName: nil)  

编译器抱怨

"Cannot convert value of type NSFetchedResultsController<NasaPicture> to expected type NSFetchedResultsController<_>"

控制器现在使用swift的通用类型，但它不会正确推断实体类型。我已明确尝试：

The controller is now using generic type for swift, but it is not inferring the entity type correctly. I've tried explicitly:

fetchedResultsController = NSFetchedResultsController<NasaPicture>(fetchRequest: request, managedObjectContext: moc, sectionNameKeyPath: nil, cacheName: nil)  

也不幸。

谢谢！

推荐答案

NSFetchRequest 现在是通用的。 NSFetchedResultsController 是一个通用的。因此，在声明变量时，必须使用一个通用声明，例如：

NSFetchRequest is now a generic. NSFetchedResultsController is a generic too. Therefore, when declaring variables, you have to use a generic declaration, e.g.:

var fetchedResultsController: NSFetchedResultsController<NasaPicture>?

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