如何从关系实体中进行简单的提取？迅速

Posted 2023-03-04

【中文标题】如何从关系实体中进行简单的提取？迅速

【英文标题】：How to make a simple fetch from relationship entities? Swift

【发布时间】：2015-08-21 18:02:13

【问题描述】：

我在 Xcode 中制作了两个关系实体，我使用的是 Swift。我在 Core Data 中建立了一个简单的关系。

公司代码

import Foundation
import CoreData

    @objc(Company)
    class Company: NSManagedObject 

        @NSManaged var nameCompany: String
        @NSManaged var additional: NSSet

    

附加代码

import Foundation
import CoreData

@objc(Additional)
class Additional: NSManagedObject 

    @NSManaged var acitvityCompany: String
    @NSManaged var founded: String
    @NSManaged var company: Company

我编写了以下代码，将数据添加到实体中。有用。

       @IBAction func saveData(sender: UIBarButtonItem) 
        var companyEntity = NSEntityDescription.insertNewObjectForEntityForName("Company", inManagedObjectContext: managedObjectContext) as! NSManagedObject
        var additionalEntity = NSEntityDescription.insertNewObjectForEntityForName("Additional", inManagedObjectContext: managedObjectContext) as! NSManagedObject

        companyEntity.setValue(nameCompanyTextField.text, forKey: "nameCompany")

        additionalEntity.setValue(activityTextField.text, forKey: "acitvityCompany")
        additionalEntity.setValue(foundedTextField.text, forKey: "founded")

        companyEntity.setValue(NSSet(object: additionalEntity), forKey: "additional")

        managedObjectContext.save(nil)

        var storyboard = UIStoryboard(name: "Main", bundle: NSBundle.mainBundle())
        var navi = storyboard.instantiateViewControllerWithIdentifier("navi") as! UINavigationController
        self.presentViewController(navi, animated: true, completion: nil)

//        println("company \(companyEntity)")
//        println("additional \(additionalEntity)")
    

当我移至显示来自实体的数据的 UITableViewController 时。如果我从附加实体获取数据，我会收到错误消息。 CoreData：致命错误：部分信息的持久缓存与当前配置不匹配。你非法改变了 NSFetchedResultsController 的获取请求、谓词或排序描述符，而没有禁用缓存或使用 +deleteCacheWithName:

如果我只从公司实体中获取数据，效果很好。

我的UITableViewController

    override func viewDidLoad() 
    super.viewDidLoad()
    self.definesPresentationContext = true 
    fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest(), managedObjectContext: managedObjectContext, sectionNameKeyPath: "nameCompany", cacheName: "nameCompany")
    fetchedResultsController.delegate = self
    fetchedResultsController.performFetch(nil)

    fetchedResultsController2 = NSFetchedResultsController(fetchRequest: fetchRequest2(), managedObjectContext: managedObjectContext, sectionNameKeyPath: "company", cacheName: "company")
    fetchedResultsController2.delegate = self
    fetchedResultsController2.performFetch(nil)


override func viewDidAppear(animated: Bool) 
    super.viewDidAppear(animated)
    self.tableView.reloadData()


// MARK: - var and let
var managedObjectContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext!

// MARK: - fetchedResultsController
var fetchedResultsController: NSFetchedResultsController!
var fetchedResultsController2: NSFetchedResultsController!

func fetchRequest() -> NSFetchRequest 
    let fetchRequest = NSFetchRequest(entityName: "Company")
    let sortDescriptor = NSSortDescriptor(key: "nameCompany", ascending: true)
    fetchRequest.fetchBatchSize = 50
    fetchRequest.predicate = nil
    fetchRequest.sortDescriptors = [sortDescriptor]
    return fetchRequest


func fetchRequest2() -> NSFetchRequest 
    let fetchRequest = NSFetchRequest(entityName: "Additional")
    let sortDescriptor = NSSortDescriptor(key: "company", ascending: true)
    fetchRequest.fetchBatchSize = 50
    fetchRequest.predicate = nil
    fetchRequest.sortDescriptors = [sortDescriptor]
    return fetchRequest


 override func numberOfSectionsInTableView(tableView: UITableView) -> Int 
    return fetchedResultsController.sections?.count ?? 0


override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int 
    return fetchedResultsController.sections?[section].numberOfObjects ?? 0


override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell 
    let cell = tableView.dequeueReusableCellWithIdentifier("cell", forIndexPath: indexPath) as! UITableViewCell

    if var dataForCell = fetchedResultsController.objectAtIndexPath(indexPath) as? Company 
        var additionalCell = fetchedResultsController2.objectAtIndexPath(indexPath) as! Additional
        cell.textLabel?.text = dataForCell.nameCompany
        cell.detailTextLabel?.text = "\(additionalCell.acitvityCompany) - \(additionalCell.founded)"
    

    return cell

【参考方案1】：

我知道怎么做。

var currentDate: NSDate!

    // MARK: - NSFetchedResultsController
    var fetchedResultsController: NSFetchedResultsController!

    func fetchRequest() -> NSFetchRequest 
        let fetchRequest = NSFetchRequest(entityName: "Car")
        let sortDescriptor = NSSortDescriptor(key: "personCar", ascending: true)
        fetchRequest.predicate = NSPredicate(format: "personRelationship.datePerson contains[c] %@", currentDate)
        fetchRequest.fetchBatchSize = 50
        fetchRequest.fetchLimit = 50
        fetchRequest.sortDescriptors = [sortDescriptor]
        println(fetchRequest)
        return fetchRequest