nsfetchedresultscontroller在swift中删除名称缓存

Question

标题已经解释了.从nsfetchedresultscontroller删除缓存的swift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()

我需要更多信息,请告诉我.

更新:

我想要这样的东西:

fetchedResultsController.deleteCacheWithName("Master")

但我不知道怎么做.

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,而不是在实例上调用:

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

如果使用缓存,则必须在更改任何获取请求,其谓词或其排序描述符之前清除缓存.或者,您可以在不使用缓存的情况下创建获取的结果控制器:

NSFetchedResultsController(..., cacheName: nil)