coreData數據操做

// 1. 創建模型文件
// 2. 創建CoreDataStack
// 3. 設置AppDelegate

 

接着

//
// CoreDataStack.swift // CoreDataStackDemo //
// Created by wangbiao on 15/10/29. // Copyright © 2015年 wangbiao. All rights reserved. //  import CoreData class CoreDataStack: NSObject { // MARK: - Properties
 let context: NSManagedObjectContext let coordinator: NSPersistentStoreCoordinator let model: NSManagedObjectModel let store: NSPersistentStore?
    
    // MARK: - Singleton
    static func defaultStack() -> CoreDataStack { return instance } fileprivate static let instance = CoreDataStack() fileprivate override init() { // 構建託管對象模型
        let bundle = Bundle.main let modelURL = bundle.url(forResource: "Test", withExtension: "momd")! model = NSManagedObjectModel(contentsOf: modelURL)!
        
        // 構建持久化存儲助理
        coordinator = NSPersistentStoreCoordinator(managedObjectModel: model) // 構建託管對象上下文，而且將助理鏈接到上下文
        context = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType) context.persistentStoreCoordinator = coordinator // 構建持久化存儲
        let manager = FileManager.default let urls = manager.urls(for: .documentDirectory, in: .userDomainMask) let documentsURL = urls.first! let storeURL = documentsURL.appendingPathComponent("Test") store = (try! coordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: storeURL, options: nil)) } // MARK: - Function
 func saveContext () { if context.hasChanges { do { try context.save() } catch { print("Save failed...") } } } }

接着實現數據操做

//新增數據
func insertStudent(sno: String, name: String, score: Int) { // 獲取上下文（也就是從」coreData基礎「裏面的那個類裏面獲取）
        let context = CoreDataStack.defaultStack().context // 構建實體對象
        let student = NSEntityDescription.insertNewObject(forEntityName: "Student", into: context) as! Student // 設置相關屬性
        student.sno = sno student.name = name student.score = score as NSNumber? } // 查詢數據
 func fetchStudents() { // 獲取上下文
        let context = CoreDataStack.defaultStack().context // 構建抓取請求
        let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Student") // 指定按照學號(sno)升序排列
        let sort = NSSortDescriptor(key: "sno", ascending: true, selector: #selector(NSString.localizedStandardCompare(_:))) request.sortDescriptors = [sort] // 構建查詢條件 // request.predicate = NSPredicate(format: "score > 60") // request.predicate = NSPredicate(format: "name like 'a*'")
        
        do { let students = (try context.fetch(request)) as! [Student] for student in students { print("\(student.sno!), \(student.name!), \(student.score!)") } } catch { print("Fetch failed...") } } // 統計信息
 func countStudents() { //        // 1. 統計分數大於90的人數 //        
//        // 獲取上下文 // let context = CoreDataStack.defaultStack().context //        
//        // 構建抓取請求 // let request = NSFetchRequest(entityName: "Student") // request.predicate = NSPredicate(format: "score > 90") // request.resultType = .CountResultType //        
// do { // let entries = (try context.executeFetchRequest(request)) // let count = entries.first!.integerValue // print("Count: \(count)") // } catch { // print("Fetch failed...") // } // 2. 計算平均分數 // 獲取上下文
        let context = CoreDataStack.defaultStack().context // 構建抓取請求
        let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Student") request.resultType = .dictionaryResultType // 指定返回結果爲字典 // 構建表達式
        let description = NSExpressionDescription() description.name = "AverageScore" let args = [NSExpression(forKeyPath: "score")] description.expression = NSExpression(forFunction: "average:", arguments: args) description.expressionResultType = .floatAttributeType // 指定返回值類型 // 將求平均值的表達式設置給request的屬性
        request.propertiesToFetch = [description] do { let entries = (try context.fetch(request)) let result = entries.first! as! NSDictionary let averageScore = result["AverageScore"]! print("Average: \(averageScore)") } catch { print("Fetch failed...") } } // 修改數據
 func updateStudents() { // 獲取上下文
        let context = CoreDataStack.defaultStack().context // 構建抓取請求
        let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Student") request.predicate = NSPredicate(format: "name like 'a*'") do { let students = (try context.fetch(request)) as! [Student] for student in students { student.score = 100 } } catch { print("Fetch failed...") } // 保存
 CoreDataStack.defaultStack().saveContext() // 備註: 批量更新 & 異步操做 ???
 } // 刪除數據
 func deleteStudents() { // 獲取上下文
        let context = CoreDataStack.defaultStack().context // 構建抓取請求
        let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Student") request.predicate = NSPredicate(format: "score < 60") do { let students = (try context.fetch(request)) as! [Student] for student in students { context.delete(student) } } catch { print("Fetch failed...") } // 保存
 CoreDataStack.defaultStack().saveContext() }

總結：

增：

1:獲取上下文

如：let context = CoreDataStack.defaultStack().context

2:構建實體對象

如：let student = NSEntityDescription.insertNewObject(forEntityName: "Student",

into: context) as! Student

3:設置相關屬性

如： student.sno = sno

4:保存數據

如：CoreDataStack.defaultStack().saveContext()

 

修改，刪除

1:獲取上下文

2:構建抓取請求

如:let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Student")

3:給抓去請求設置相關屬性吧

如：

//至關於給它設置約束

request.predicate = NSPredicate(format: "name like 'a*'")

// 指定返回結果爲字典（修改，刪除通常不用設置這個）

request.resultType = .dictionaryResultType

4:執行抓取操做

do {

let students = (try context.fetch(request)) as! [Student]

for student in students {

//修改如：student.score = 100

//刪除如：context.delete(student)

}

} catch {

print("Fetch failed...")

}

5:保存數據

 

查詢

1:獲取上下文

2:構建抓取請求

3:指定按照學號(sno)升序排列（其實此部能夠省略）

let sort = NSSortDescriptor(key: "sno", ascending: true,

selector: #selector(NSString.localizedStandardCompare(_:)))

request.sortDescriptors = [sort]

4:執行抓取語句

do {

let students = (try context.fetch(request)) as! [Student]

for student in students {

print("\(student.sno!), \(student.name!), \(student.score!)")

}

} catch {

print("Fetch failed...")

}

5:釋放資源

 

統計

1:獲取上下文

2:構建抓取請求

3:指定按照學號(sno)升序排列（其實此部能夠省略）

let sort = NSSortDescriptor(key: "sno", ascending: true,

selector: #selector(NSString.localizedStandardCompare(_:)))

request.sortDescriptors = [sort]

4: 構建表達式(average是聚合函數，固然還有其餘的)

如：let description = NSExpressionDescription()

description.name = "AverageScore"

let args = [NSExpression(forKeyPath: "score")]

description.expression = NSExpression(forFunction: "average:", arguments: args)

description.expressionResultType = .floatAttributeType // 指定返回值類型

5:將求平均值的表達式設置給request的屬性

如request.propertiesToFetch = [description]

4:執行抓取語句

do {

let entries = (try context.fetch(request))

let result = entries.first! as! NSDictionary

let averageScore = result["AverageScore"]!

print("Average: \(averageScore)")

} catch {

print("Fetch failed...")

}

5:釋放資源

 

固然，這個只是一個例子而已，不是全部的統計例子都要那麼複雜的

以下面這個例子

// 1. 統計分數大於90的人數

//

// // 獲取上下文

// let context = CoreDataStack.defaultStack().context

//

// // 構建抓取請求

// let request = NSFetchRequest(entityName: "Student")

// request.predicate = NSPredicate(format: "score > 90")

// request.resultType = .CountResultType

//

// do {

// let entries = (try context.executeFetchRequest(request))

// let count = entries.first!.integerValue

// print("Count: \(count)")

// } catch {

// print("Fetch failed...")

// }