如何在swift

Question

我有3个类似的表，我想存储在核心数据中。我想使用NSFetchedResultsController从公共视图控制器查看和编辑表。如何概括设置或使用子类来实现此目的？我的代码中的敌人示例如下所示

  

建议

是其中一个实体。我有另一个名为

的实体

  

结果

我想使用（通过更改表中的单元格描述）并进行适当的其他更改。例如，我如何用变量表示Recommendation。

var moc:NSManagedObjectContext!
var fetchedResultsController: NSFetchedResultsController<Recommendation>!
var recommendations: [Recommendation] = []

和方法：

    func setupFetchedResultsController() {
    let dataRequest:NSFetchRequest<Recommendation> = Recommendation.fetchRequest()
    let sortDescriptor = NSSortDescriptor(key:"recordNumber", ascending: true)
    dataRequest.sortDescriptors = [sortDescriptor]

    fetchedResultsController = NSFetchedResultsController(fetchRequest: dataRequest, managedObjectContext: moc, sectionNameKeyPath: #keyPath(Recommendation.recordNumber), cacheName: nil)
    fetchedResultsController.delegate = self
    do {
        try fetchedResultsController.performFetch()
    } catch {
        print(error.localizedDescription)
    }
}

Answer 1

您可以创建一个基本表视图控制器，其中包含要重写的属性。我建议像核心数据模板中建议的那样懒惰地初始化fetch控制器。

class BaseTableViewController: UITableViewController {

    var managedObjectContext : NSManagedObjectContext!

    // MARK: - Variables to be overridden

    var entity : String { fatalError("entity must be overridden") }
    var sortDescriptors : [NSSortDescriptor]? { return nil }
    var cacheName : String? { return nil }
    var sectionNameKeyPath : String? { return nil }
    var fetchPredicate : NSPredicate? {
        didSet {
            fetchedResultsController.fetchRequest.predicate = fetchPredicate
        }
    }

   ...

    lazy var fetchedResultsController: NSFetchedResultsController<NSFetchRequestResult> = {

        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: self.entity)
        fetchRequest.predicate = self.fetchPredicate

        fetchRequest.sortDescriptors = self.sortDescriptors
        let aFetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest,
                                                               managedObjectContext: self.managedObjectContext!,
                                                               sectionNameKeyPath: self.sectionNameKeyPath,
                                                               cacheName: self.cacheName)
        aFetchedResultsController.delegate = self

        do {
            try aFetchedResultsController.performFetch()
        } catch let error as NSError {
            self.present(error:error)
        }

        return aFetchedResultsController
    }()

   ...

}

现在您可以继承控制器

class RecommendationViewController: BaseTableViewController {

  // MARK: - Variables to overide

  override var entity : String { return "Recommendation" }
  override var sectionNameKeyPath : String? { return #keyPath(Recommendation.recordNumber) }
  override var sortDescriptors : [NSSortDescriptor]? { return [NSSortDescriptor(key:"recordNumber", ascending: true)] }