swift - nsfetchedresultscontroller 在 swift 中删除具有名称的缓存

Question

标题已经说明了。从 nsfetchedresultscontroller 中删除缓存的快速代码是什么。

这是我得到的错误:

You have illegally mutated the NSFetchedResultsController's fetch request, its predicate, or its sort descriptor without either disabling caching or using +deleteCacheWithName:'

和代码:

if arranged == "naam - A-Z" {
            let sortDescriptor = NSSortDescriptor(key: "name", ascending: true)
            self.fetchedResultsController.fetchRequest.sortDescriptors = [sortDescriptor]
        }else if arranged == "naam - Z-A" {
            let sortDescriptor = NSSortDescriptor(key: "name", ascending: false)
            self.fetchedResultsController.fetchRequest.sortDescriptors = [sortDescriptor]
        }else if arranged == "gemiddelde - 1-10" {
            let sortDescriptor = NSSortDescriptor(key: "gemiddelde", ascending: true)
            self.fetchedResultsController.fetchRequest.sortDescriptors = [sortDescriptor]
        }else if arranged == "gemiddelde - 10-1" {
            let sortDescriptor = NSSortDescriptor(key: "gemiddelde", ascending: false)
            self.fetchedResultsController.fetchRequest.sortDescriptors = [sortDescriptor]
        }

        do {
            try _fetchedResultsController!.performFetch()
        } catch {
            // Replace this implementation with code to handle the error appropriately.
            // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
           // print("Unresolved error \(error), \(error.userInfo)")
            abort()
        }
        tableView.reloadData()

如果您需要更多信息，请告诉我。

更新:

我想要这样的东西:

fetchedResultsController.deleteCacheWithName("Master")

但是我不知道怎么办。

Answer 1

fetchedResultsController.deleteCacheWithName("Master")

不编译因为

public class func deleteCacheWithName(name: String?)

是一个类型函数，它必须在类型(类)本身上调用，不在实例上:

// Swift 2:
NSFetchedResultsController.deleteCacheWithName("Master")
// Swift 3:
NSFetchedResultsController<NSFetchRequestResult>.deleteCache(withName: "Master")

如果您正在使用缓存，则必须在更改任何提取请求、其谓词或其排序描述符之前清除缓存。或者，您可以创建获取的结果 Controller 不使用缓存:

NSFetchedResultsController(..., cacheName: nil)