介绍

• Core Data 的继承者，使用声明式的语法进行数据的持久化操作。
• 支持 CloudKit 同步，并且与 Core Data 兼容。

使用步骤

1. 导入模块import SwiftData。
2. 使用@Model修饰模型。
3. 将模型注册到ModelContainer。
4. 获取模型上下文ModelContext。
5. 通过模型上下文进行增删改查（CRUD）操作。

案例

import Foundation
import SwiftData
import UIKit

@Model
class User: CustomStringConvertible {
    var id: UUID
    var name: String
    var company: Company

    init(name: String, company: Company) {
        id = UUID()
        self.name = name
        self.company = company
    }

    var description: String {
        return "\(name)—\(company.name)—\(company.address)"
    }
}

@Model
class Company {
    @Attribute(.unique)
    var id: String
    var name: String
    var address: String

    init(id: String, name: String, address: String) {
        self.id = id
        self.name = name
        self.address = address
    }
}



class DataTools {
    static var shared = DataTools()
    var container: ModelContainer?
    var context: ModelContext?

    init() {
        do {
            container = try ModelContainer(for: [User.self, Company.self])
            if let container {
                context = ModelContext(container)
            }
        } catch {
            print(error)
        }
    }

    // 增加
    func insert(user: User) {
        context?.insert(object: user)
    }

    // 删除
    func delete(user: User) {
        context?.delete(object: user)
    }

    // 修改
    func update(user: User, newCompanyName: String, newCompanyAddress: String) {
        user.company.name = newCompanyName
        user.company.address = newCompanyAddress
    }

    // 查询
    func select(completionHandler: @escaping ([User]?, Error?) -> Void) {
        let descriptor = FetchDescriptor<User>(sortBy: [SortDescriptor<User>(\.name)])
        do {
            let data = try context?.fetch(descriptor)
            completionHandler(data, nil)
        } catch {
            completionHandler(nil, error)
        }
    }

    // 保存
    func save() {
        do {
            try context?.save()
        } catch {
            print(error.localizedDescription)
        }
    }
}



class ViewController: UIViewController {
    var dataTools = DataTools.shared
    var users = [User]()

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    @IBAction func insertData(_ sender: Any) {
        let user1 = User(name: "张三", company: Company(id: "1", name: "百度", address: "中国北京"))
        let user2 = User(name: "李四", company: Company(id: "2", name: "阿里巴巴", address: "浙江杭州"))
        let user3 = User(name: "王五", company: Company(id: "3", name: "腾讯", address: "广东深圳"))
        dataTools.insert(user: user1)
        dataTools.insert(user: user2)
        dataTools.insert(user: user3)
    }

    @IBAction func deleteData(_ sender: Any) {
        if let user = users.last {
            dataTools.delete(user: user)
        }
    }

    @IBAction func updateData(_ sender: Any) {
        if let user = users.first {
            dataTools.update(user: user, newCompanyName: "美团", newCompanyAddress: "中国北京")
        }
    }

    @IBAction func selectData(_ sender: Any) {
        dataTools.select { data, error in
            if let error {
                print(error)
            }
            if let data {
                self.users = data
                print(self.users)
            }
        }
    }
}