如何过滤在 Core Data 中有对象的表视图？
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【中文标题】如何过滤在 Core Data 中有对象的表视图？【英文标题】：How can I filter my tableview that has objects in Core Data? 【发布时间】：2017-07-30 03:05:27 【问题描述】：我正在创建一个联系人应用程序，到目前为止，我已经成功地将项目保存到我的 tableview 中。我有一个搜索栏，我想按名字过滤掉我的单元格，我知道因为我在核心数据中工作，所以我必须使用 fetchResultsController 和 NSPredicate。我很难弄清楚这些东西，也许有人可以帮助我？
这也是我的核心数据实体，以防万一。
实体：联系人
属性：
名字，字符串 姓氏，字符串 出生日期，字符串 电话号码，字符串 邮政编码，字符串我知道有些代码可能不完整，但我只需要指导如何使用它。我只想让用户输入一个名字，它会按名字过滤单元格。如果您需要更多信息，请告诉我。
现在这是我的 ContactsTableVC 中的代码：
import UIKit
import CoreData
class ContactsTableVC: UITableViewController, UISearchBarDelegate, NSFetchedResultsControllerDelegate
@IBOutlet weak var searchBar: UISearchBar!
var isFiltered: Bool = false
//Holds the core data model
var persons: [Person] = []
override func viewDidLoad()
super.viewDidLoad()
searchBar.delegate = self
self.tableView.separatorStyle = UITableViewCellSeparatorStyle.none
self.tableView.backgroundColor = UIColor(red: 240/255.0, green: 240/255.0, blue: 240/255.0, alpha: 1.0)
fetch()
self.tableView.reloadData()
func getContext () -> NSManagedObjectContext
let appDelegate = UIApplication.shared.delegate as! AppDelegate
return appDelegate.persistentContainer.viewContext
// MARK: - Searchbar
//add fetchrequest to did ebgin editing
func searchBarTextDidBeginEditing(_ searchBar: UISearchBar)
func searchBarTextDidEndEditing(_ searchBar: UISearchBar)
if(searchBar.text == "")
isFiltered = false
else
isFiltered = true
func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String)
filter(text: searchText)
// MARK: - Fetchresults controller / filtering data
func filter(text: String)
//Create fetch request
let fetchRequest = NSFetchRequest<Person>()
// guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else return replaced with getcontext
// let managedObjectContext = appDelegate.persistentContainer.viewContext
let entity = NSEntityDescription.entity(forEntityName: "Contact", in: getContext())
fetchRequest.entity = entity
let sortDescriptor = NSSortDescriptor(key: "firstName", ascending: false)
let sortDescriptors: [Any] = [sortDescriptor]
fetchRequest.sortDescriptors = sortDescriptors as? [NSSortDescriptor] ?? [NSSortDescriptor]()
if(text.characters.count > 0)
let predicate = NSPredicate(format: "(firstName CONTAINS[c] %@)", text)
fetchRequest.predicate = predicate
let loadedEntities: [Person]? = try? getContext().fetch(fetchRequest)
filteredContacts = [Any](arrayLiteral: loadedEntities) as! [Person]
self.tableView.reloadData()
// MARK: - Data Source
func fetch()
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else return
let managedObjectContext = appDelegate.persistentContainer.viewContext
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName:"Contact")
do
persons = try managedObjectContext.fetch(fetchRequest) as! [Person] //NSManagedObject
catch let error as NSError
print("Could not fetch. \(error)")
func save(firstName: String, lastName: String, dob: String, phoneNumber: String, zipCode: String)
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else return
let managedObjectContext = appDelegate.persistentContainer.viewContext
guard let entity = NSEntityDescription.entity(forEntityName:"Contact", in: managedObjectContext) else return
let person = NSManagedObject(entity: entity, insertInto: managedObjectContext)
person.setValue(firstName, forKey: "firstName")
person.setValue(lastName, forKey: "lastName")
person.setValue(dob, forKey: "dateOfBirth")
person.setValue(phoneNumber, forKey: "phoneNumber")
person.setValue(zipCode, forKey: "zipCode")
do
try managedObjectContext.save()
self.persons.append(person as! Person) //previously just contact, no casting!
catch let error as NSError
print("Couldn't save. \(error)")
func update(indexPath: IndexPath, firstName: String, lastName: String, dob: String, phoneNumber: String, zipCode: String)
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else return
let managedObjectContext = appDelegate.persistentContainer.viewContext
let contact = persons[indexPath.row]
contact.setValue(firstName, forKey: "firstName")
contact.setValue(lastName, forKey: "lastName")
contact.setValue(dob, forKey: "dateOfBirth")
contact.setValue(phoneNumber, forKey: "phoneNumber")
contact.setValue(zipCode, forKey: "zipCode")
do
try managedObjectContext.save()
persons[indexPath.row] = contact
catch let error as NSError
print("Couldn't update. \(error)")
func delete(_ contact: NSManagedObject, at indexPath: IndexPath)
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else return
let managedObjectContext = appDelegate.persistentContainer.viewContext
managedObjectContext.delete(contact)
persons.remove(at: indexPath.row)
//Always remember to save after deleting, updates Core Data
do
try managedObjectContext.save()
catch
print("Something went wrong \(error.localizedDescription)")
// MARK: - Table View Setup
override func numberOfSections(in tableView: UITableView) -> Int
return 1
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int
return persons.count
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell
let cell = tableView.dequeueReusableCell(withIdentifier: "ContactCell", for: indexPath) as? PersonsCell
let person = persons[indexPath.row]
cell?.firstName?.text = person.value(forKey:"firstName") as? String
cell?.lastName?.text = person.value(forKey:"lastName") as? String
cell?.dob?.text = person.value(forKey:"dateOfBirth") as? String
cell?.phoneNumber?.text = person.value(forKey:"phoneNumber") as? String
cell?.zipCode?.text = person.value(forKey:"zipCode") as? String
return cell!
override func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat
return 75
// Override to support conditional editing of the table view.
override func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool
return true
// MARK: - Navigation
@IBAction func unwindToContactsList(segue:UIStoryboardSegue)
if let viewController = segue.source as? AddContactVC
guard let _firstName: String = viewController.firstNameLbl.text,
let _lastName: String = viewController.lastNameLbl.text,
let _dob: String = viewController.dateOfBirthLbl.text,
let _phoneNumber: String = viewController.phoneNumberLbl.text,
let _zipCode: String = viewController.zipCodeLbl.text
else return
if _firstName != "" && _lastName != "" && _dob != "" && _phoneNumber != "" && _zipCode != ""
if let indexPath = viewController.indexPathForContact
update(indexPath: indexPath, firstName: _firstName, lastName: _lastName, dob: _dob, phoneNumber: _phoneNumber, zipCode: _zipCode)
print("Any updates?")
else
save(firstName: _firstName, lastName: _lastName, dob: _dob, phoneNumber: _phoneNumber, zipCode: _zipCode)
print("added to tableview") //this runs twice for some reason...
tableView.reloadData()
else if let viewController = segue.source as? EditContactVC
if viewController.isDeleted
guard let indexPath: IndexPath = viewController.indexPath else return
let person = persons[indexPath.row]
delete(person, at: indexPath)
tableView.reloadData()
【问题讨论】：
【参考方案1】：这里是使用NSFetchedResultsController 实现目标的示例代码。我省略了一些不相关的代码。
class ContactViewController: UITableViewController
let fetchedResultsController: NSFetchedResultsController<Contact>!
func searchTextFieldDidEditingChanged(_ textField: UITextField)
let text = textField.text ?? ""
refetch(with: text)
// The key is you need change the predicate when searchTextField's
// value changed, and invoke proformFetch() again
func refetch(with text: String)
let predicate = NSPredicate(format: "firstName CONTAINS %@", text)
fetchedResultsController.fetchRequest.predicate = predicate
do
try self.fetchedResultsController.performFetch()
tableView.reloadData()
catch let error as NSError
loggingPrint("Error: \(error.localizedDescription)")
// MARK: - Table datasource
extension ContactViewController
override func numberOfSections(in tableView: UITableView) -> Int
return fetchedResultsController.sections!.count
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int
let sectionInfo = fetchedResultsController.sections![section]
return sectionInfo.numberOfObjects
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell
let cell = tableView.dequeueReusableCell(withIdentifier: "ContactCell", for: indexPath) as? PersonsCell
let contact = fetchedResultsController.object(at: indexPath)
cell.contact = contact
return cell!
【讨论】：
【参考方案2】：您可以使用 NSPredicate 的sortDescriptors 属性来过滤获取请求的结果。
查看链接了解更多信息： How to sort a fetch in Core Data
【讨论】：
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