swift3 CoreData增删改查

swift3 CoreData的操作十分简单，只需要简单的几个步骤就能完成增删改查

要使用CoreData，需要在新建项目时勾选CoreData选项

新建的项目中会有SwiftDemo2.xcdatamodeld这个文件(SwiftDemo2是项目名)

新增一个entity(相当于数据库的表)，添加entity的属性，如下图我新增了一名为"Note"的entity

增

func saveData(content:String){
        let appDelegate: AppDelegate = UIApplication.shared.delegate as! AppDelegate
        let context:NSManagedObjectContext = appDelegate.persistentContainer.viewContext
        
        let note: Note = Note(context: context)
        note.content = content
        note.createTime = NSDate()
        
        appDelegate.saveContext()
    }

appDelegate.saveContext()是在AppDelegate.swift里自动生成的

这里的Note类是自动生成的，默认情况下类名与entity名相同，可以在新增entity的时候指定对应的类名

查

func getData() -> [Note] {
        let appDelegate: AppDelegate = UIApplication.shared.delegate as! AppDelegate
        let context:NSManagedObjectContext = appDelegate.persistentContainer.viewContext
        
        var dataList: [Note] = []
        let fetchRequest: NSFetchRequest = Note.fetchRequest()
//        let predicate = NSPredicate(format: "content='aa'") //增加查询条件
//        fetchRequest.predicate = predicate
        do {
            dataList = try context.fetch(fetchRequest)
        } catch {
            print(error)
        }
        
        return dataList
    }

改

func updateData(object:Note,content:String) {
        let appDelegate: AppDelegate = UIApplication.shared.delegate as! AppDelegate
        
        object.content = content
        appDelegate.saveContext()
    }

删

func deleteData(object:Note) {
        let appDelegate: AppDelegate = UIApplication.shared.delegate as! AppDelegate
        let context:NSManagedObjectContext = appDelegate.persistentContainer.viewContext
        context.delete(object)
        appDelegate.saveContext()
    }

如果用tableview展示数据，使用上面方法，增加或更新一条数据列表就要重新载入全部数据，性能不好

NSFetchedResultsController可把单元格内容与数据进行绑定，响应数据变化

需要遵从NSFetchedResultsControllerDelegate协议，具体代码如下：

import UIKit
import CoreData

class NoteTableController: UITableViewController,NSFetchedResultsControllerDelegate {
    
    var dataSource:[Note] = [Note]()
    var fc:NSFetchedResultsController!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 加载全部数据
        let request:NSFetchRequest! = Note.fetchRequest()
        let sd = NSSortDescriptor(key: "createTime", ascending: true) // 指定结果如何排序
        request.sortDescriptors = [sd]
        let appDelegate = UIApplication.shared.delegate as! AppDelegate
        let context = appDelegate.persistentContainer.viewContext
        fc = NSFetchedResultsController(fetchRequest: request, managedObjectContext: context, sectionNameKeyPath: nil, cacheName: nil)
        fc.delegate = self
        
        do {
            try fc.performFetch()
            if let results = fc.fetchedObjects {
                dataSource = results
            }
        } catch {
            print(error)
        }
        
    }
    
    func controllerWillChangeContent(_ controller: NSFetchedResultsController) {
        tableView.beginUpdates()
    }
    
    func controllerDidChangeContent(_ controller: NSFetchedResultsController) {
        tableView.endUpdates()
    }
    
    func controller(_ controller: NSFetchedResultsController, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
        switch type {
        case NSFetchedResultsChangeType.delete:
            tableView.deleteRows(at: [indexPath!], with: UITableViewRowAnimation.automatic)
        case NSFetchedResultsChangeType.insert:
            // 新增一条数据后在列表增加一行，不用重新载入全部数据
            tableView.insertRows(at: [newIndexPath!], with: UITableViewRowAnimation.automatic)
        case NSFetchedResultsChangeType.update:
            tableView.reloadRows(at: [indexPath!], with: UITableViewRowAnimation.automatic)
        default:
            tableView.reloadData()
        }
        
        if let objects = controller.fetchedObjects {
            dataSource = objects as! [Note]
        }
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
    
    // MARK: - Table view data source
    
    override func numberOfSections(in tableView: UITableView) -> Int {
        // #warning Incomplete implementation, return the number of sections
        return 1
    }
    
    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        // #warning Incomplete implementation, return the number of rows
        return dataSource.count
    }
    
    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        var cell:UITableViewCell? = tableView.dequeueReusableCell(withIdentifier: "rowId")
        if cell == nil {
            cell = UITableViewCell(style: UITableViewCellStyle.default, reuseIdentifier: "rowId")
        }
        
        cell!.textLabel?.text = dataSource[indexPath.row].content
        
        return cell!
    }
    
    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        let editView:AddNoteViewController? = self.storyboard?.instantiateViewController(withIdentifier: "editView") as? AddNoteViewController
        editView?.editNote = dataSource[indexPath.row]
        editView?.editContent = dataSource[indexPath.row].content
        self.navigationController?.pushViewController(editView!, animated: true)
    }
    
    override func tableView(_ tableView: UITableView, editingStyleForRowAt indexPath: IndexPath) -> UITableViewCellEditingStyle {
        return UITableViewCellEditingStyle.delete
    }
    
    // Override to support editing the table view.
    override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
        if editingStyle == .delete {
            let appDelegate = UIApplication.shared.delegate as! AppDelegate
            let context = appDelegate.persistentContainer.viewContext
            context.delete(self.fc.object(at: indexPath))
            appDelegate.saveContext()
        }
    }
    
    override func viewWillAppear(_ animated: Bool) {
        tableView.reloadData()
        tableView.isEditing = false
        editBtn.title = "编辑"
    }
    
    
    @IBOutlet weak var editBtn: UIBarButtonItem!
    @IBAction func edit(_ sender: UIBarButtonItem) {
        if tableView.isEditing {
            tableView.isEditing = false
            editBtn.title = "编辑"
        } else {
            tableView.isEditing = true
            editBtn.title = "完成"
        }
    }
    
}

import UIKit
import CoreData

class AddNoteViewController: UIViewController,UITextViewDelegate {
    
    @IBOutlet weak var editTextView: UITextView!
    var editNote:Note?
    var editContent:String?
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // textview前面不留空行
        self.automaticallyAdjustsScrollViewInsets = false
        
        if editContent != nil {
            editTextView.text = editContent
        }
        
        // 监听键盘打开和收起事件
        NotificationCenter.default.addObserver(self, selector: #selector(AddNoteViewController.keyboardWillShow), name: NSNotification.Name.UIKeyboardWillShow, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(AddNoteViewController.keyboardWillHide), name: NSNotification.Name.UIKeyboardWillHide, object: nil)
    }
    
    @IBAction func complete(_ sender: Any) {
        // 收起键盘
        editTextView.endEditing(true)
    }
    
    @IBAction func saveNote(_ sender: Any) {
        let appDelegate: AppDelegate = UIApplication.shared.delegate as! AppDelegate
        if editNote != nil { // 更新
            editNote?.content = editTextView.text
        }else{ // 新增一条记录
            let context:NSManagedObjectContext = appDelegate.persistentContainer.viewContext
            let note: Note = Note(context: context)
            note.content = editTextView.text
            note.createTime = NSDate()
        }
        
        appDelegate.saveContext()
        
        self.navigationController?.popViewController(animated: true)
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
    
    func keyboardWillShow(notification:NSNotification){
        // 输入位置被键盘挡住时上移
        let keyboardRect = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue
        if keyboardRect != nil {
            self.editTextView.contentInset.bottom = keyboardRect!.height
        }
    }
    
    func keyboardWillHide(notification:NSNotification){
        // 输入框恢复原位
        self.editTextView.contentInset.bottom = 0
    }
    
}